Our own product
Writford
A workspace for UK legal firms connecting cited research, matter records, time recording and billing. The research workflow keeps source checking and professional review with the solicitor.
Explore WritfordSoftware Delivery
Mobile App Development
iOS and Android apps on React Native, or fully native where that genuinely serves you better, with AI features built in where they add value rather than bolted on for a demo. BigBerri builds them for UK businesses on accounts you own, with a fixed price quoted after a free discovery call.
- MVP app live in 6–10 weeks
- Fixed price, never a day rate
- Automated tests on every build
- Developer accounts in your name
Or call 07305 694001.
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Smart Search
Android
What We Build
AI-Native Mobile Apps
Every app we build is AI-ready from the ground up — not retrofitted after launch.
Cross-Platform (iOS & Android)
React Native apps that run natively on both platforms from one codebase — faster to build, cheaper to maintain.
AI Features Built In
Chatbots, voice commands, smart search, recommendations, image recognition — AI from day one, not bolted on later.
Secure & Scalable Backend
Node.js or Laravel APIs, user authentication, push notifications, real-time data, and cloud hosting on AWS or GCP.
App Store Launch
Full submission to Apple App Store and Google Play — including screenshots, descriptions, and App Store Optimisation.
The Stack
What it is actually built on
Named plainly, because a mainstream stack is what lets another developer pick up the app if you ever need one to. Nothing here is proprietary to us, and nothing locks you to a platform only we understand.
Cross-platform
- React Native
- Expo and EAS Build
- TypeScript throughout
Fully native
- Swift and SwiftUI (iOS)
- Kotlin and Jetpack Compose (Android)
- Used where React Native genuinely cannot
Backend & data
- Node.js or Laravel APIs
- PostgreSQL
- AWS or Google Cloud hosting
Testing & CI
- Jest and React Native Testing Library for unit tests
- Maestro or Detox for end-to-end testing
- GitHub Actions running every build
Release & delivery
- Fastlane for store deployment
- TestFlight and Play Console internal tracks
- EAS Update for over-the-air fixes between releases
AI, where it earns its place
- Chat and voice via the same stack as our AI services
- On-device where privacy or offline use matters
- Never added as a checkbox feature
Scope
What a Project Looks Like
Every project is scoped and quoted after a free discovery call, so you get a fixed price for your situation rather than a number that assumes someone else’s. These are the shapes most engagements take.
MVP App
Testing one core journey on iOS and Android before investing further.
Typical timeline: 6–10 weeks
- iOS and Android from one codebase
- Core user journey only
- App Store and Play submission
- Analytics and crash reporting
Most common
Full Product App
A product with accounts, payments and notifications that needs regular releases.
Typical timeline: 10–16 weeks
- Accounts, payments, notifications
- AI features (chat, voice, vision)
- Backend and admin panel
- Ongoing releases
Enterprise App
Complex integrations, offline working and formal security review.
Typical timeline: 16+ weeks
- Complex integrations and offline mode
- Security and compliance reviews
- Multi-region infrastructure
- SLA-backed support
Timelines are typical and depend on how many systems are involved and how ready your data is. Tell us what you need and we will give you a fixed price and a date.
The Build
What the weeks actually look like
This is a typical MVP-tier build. A full-product app with accounts and payments runs longer; an enterprise app with offline mode and formal security review longer still. The column on the right is the part most proposals leave out: a mobile project stalls on decisions and access far more often than on the engineering.
| When | What we do | What we need from you |
|---|---|---|
| Weeks 1–2Scope, design and architecture | We define the screens, the user flows and the backend the app needs, agree the tier and the stack, and produce wireframes and an interactive prototype for sign-off before any production code is written. | A named decision-maker, any existing brand or Figma assets, and sign-off on the prototype before the build starts. |
| Weeks 3–6Build in sprints | Frontend, backend and any AI features built in parallel with a weekly demo, so you see working software early rather than at the end. Automated tests run on every build through CI from day one, not bolted on before launch. | A short weekly review of the demo, and quick answers when a design or scope question comes up mid-sprint. |
| Weeks 7–8Test on real devices and submit | QA on physical iOS and Android devices, not only simulators, plus edge-case and security review. We prepare and submit to the App Store and Google Play, including the account verification and closed-testing steps each platform requires. | Two or three people to try to break it, and the developer accounts created in your company’s name. |
| After launchWatch and support | We monitor crash reports and store reviews in the opening weeks and fix what the first real users find. Ongoing platform updates and store submissions continue under the support arrangement agreed before launch. | A decision on the ongoing support level once the app is live. |
The Boundary
What it must never do
A mobile app holds a closer relationship with a user than a website does — it sits on their device, asks for permissions, and often touches payment and personal data. So there are things we build in as non-negotiable rather than leave to a checklist at the end.
Some of this is store policy, some is good engineering, and all of it is cheaper to build in from week one than to retrofit after a rejection or a complaint.
- Store a payment card number directly — card handling runs through a compliant provider, never our own database
- Request a device permission the app does not actually use
- Ship without crash reporting — a bug in production should be visible the day it happens, not the day a user complains
- Submit a privacy label to the App Store or Play Store that does not match what the app actually collects
- Skip accessibility — screen reader support and touch target sizing are built in, not retrofitted after a complaint
- Leave the app unable to update — over-the-air fixes are part of the build, not an afterthought
Our Process
Design to App Store
01
Scope & Design
Define screens, user flows, and features. UI/UX wireframes and interactive prototype for sign-off.
02
Build
Sprint-based development with weekly demos. Frontend, backend, and AI features built in parallel.
03
Test
QA testing on real devices, edge case testing, performance profiling, and security review.
04
Launch & Support
App Store and Google Play submission. Monitoring, bug fixes, and ongoing feature development.
After Launch
How handover and support work
An app is something you live with for years, not a one-off delivery, so the arrangement is built to survive the end of the engagement rather than depend on it.
Accounts in your name
The Apple Developer, Google Play Console and any backend hosting accounts are registered to your company from day one, with us as an invited team member. Ending the relationship means removing a user, not migrating a store listing.
What you receive
The full source code and repository, the CI configuration, the design files, and documentation another developer can actually work from — not a code dump with no explanation.
The first weeks
We watch crash reports and store reviews closely once real users are on the app, because the bugs a launch surfaces are rarely the ones QA found. Fixes ship quickly while you are watching, not at a quarterly review.
After that
Optional ongoing support covering OS updates, store resubmissions and new features. Agreed before launch: what is covered, how quickly we respond, and what counts as new work rather than maintenance.
Who It's For
Where a mobile app earns its place
Not every business needs an app — a website people can save to their home screen is often the better first move, and we will say so on the call. Where a native app genuinely earns its place, these are the sectors we see it most.
Not sure whether you need an app or a web application? Our guide to native, cross-platform or web sets out the decision, and what actually drives the cost.
FAQ
The questions people ask before hiring us
React Native, or a fully native app — how do you decide?
React Native for most apps: one codebase, native performance on both stores, and a faster route to launch. We build natively in Swift or Kotlin when the app needs something React Native genuinely cannot do well — heavy graphics, deep hardware access, or a long-lived product with a dedicated team per platform. We check which situation yours is on the discovery call rather than defaulting to whichever we would rather build. Our guide to [native, cross-platform or web](/blog/native-vs-cross-platform-app-uk) sets out the decision in full.
Do you test on real devices, or just simulators?
Both, and the real devices matter more than people expect — a simulator will not catch a camera permission prompt behaving oddly on one specific Android skin, or a push notification arriving late on an older iPhone. Automated tests run on every build through CI; a final pass runs on physical devices before anything ships to the stores.
Can you add AI features to a mobile app?
Yes, where it earns its place rather than as a bullet point. Chatbots, voice input, smart search and recommendation are the common ones, built the same way we build [AI chatbots](/services/ai-chatbot-development) and [AI integrations](/services/ai-integration) for the web — same team, same standards, connected to your app’s backend rather than bolted on as a separate service.
Do you handle App Store and Google Play submission?
Yes, including the parts that catch people out. Apple’s own App Review page states ninety per cent of submissions are reviewed in under twenty-four hours, but rejections — most often guideline 2.1, App Completeness — restart that clock, so we build against the checklist rather than hoping it passes first time. Google Play requires new personal developer accounts to run a closed test with twelve testers for fourteen days before production access, which is one of several reasons the accounts are set up in your company’s name rather than a founder’s from day one.
Who owns the app and the developer accounts?
You do. The Apple and Google developer accounts are set up in your company name rather than ours, and the code is yours on completion and full payment. This is the single most important question to ask an app developer: if the accounts are theirs, leaving means rebuilding your store presence and losing your reviews and ranking history, which is a far more expensive lock-in than the code.
What happens when the platforms change the rules?
They will, regularly — new OS versions, new store requirements, new compliance obligations. An app that is not maintained stops working eventually rather than gradually. We agree a support arrangement covering platform updates and store submissions, and we tell you plainly what falls outside it. Building without any allowance for this is the most common reason an app quietly dies in its second year.
How do we know you will still be here in two years?
You should not have to bet on it. React Native, Swift and Kotlin are mainstream platforms any competent developer can pick up, the code is yours, and the accounts are yours — nothing about the app depends on us personally remaining available. Big Berri Limited is registered in England and Wales, company number 16562429, and ICO registered under ZC119995, both of which you can check.
Guides
Read before you buy mobile app development
- Mobile Development
Native, Cross-Platform or Web App? What UK Businesses Should Decide Before Commissioning
The stack matters less than most agencies pretend. What actually decides it, and the four UK and EU obligations that catch businesses after the app is already built.
- MVP Development
What Decides What It Costs to Build an App in the UK? A 2026 Guide
A straight answer on what drives app development cost for UK businesses in 2026 — the scope decisions that matter, the features that move a quote up or down, the ongoing costs nobody mentions on the sales call, and how UK agencies compare with freelancers and offshore teams.
- AI Development
Hire an AI Developer or Use an Agency? A UK Decision Guide for 2026
Employing an AI engineer, bringing in a contractor and hiring an agency are three different commitments with three different risks. What changed in UK employment law in 2026, and how to decide.
- AI Services
AI Development Cost UK: The Real 2026 Pricing Guide
What actually drives AI development cost in the UK for chatbots, voice agents, automation, integration, web apps, mobile apps and MVPs — plus offshore comparisons and the questions to ask before you sign a quote.
Before You Get In Touch
What you can hold us to
Review our own live products, check our company registrations and read the commitments that shape a project. These give you concrete work and clear terms to discuss before booking a call.
Our own product
Let AI Browse
Tools for connecting shopping assistants with storefront product, cart and checkout actions. Its WordPress and storefront integrations show the kind of connected web workflows we build.
Explore Let AI BrowseRead the LetAIBrowse case studyWhat the discovery call actually is
Thirty minutes, free, no obligation and no salesperson. You describe what is costing you time or customers, we ask about the systems involved, and you leave with an honest view of whether this is worth doing. We regularly end that call by saying the tool you already pay for covers it.
You own the result
The code, the repository and the accounts are set up in your company name rather than ours, and they are yours on completion and full payment. Nothing runs on infrastructure we control, so ending the relationship does not end the thing we built.
A fixed price, never a day rate
Every project is quoted as a fixed price with a written scope after the call, so an over-run is our problem rather than yours. If the scope changes, we say so and re-quote before doing the work, not after.
Where your data sits
In the UK or EU, under a data processing agreement, kept only as long as you specify. Any model provider we rely on is named as a sub-processor rather than left implicit, and we will tell you plainly where something you have asked for would put a commitment of yours at risk.
What happens when it goes wrong
Agreed before launch rather than negotiated during an incident: what is covered, how quickly we respond, and what counts as new work. Every build has a defined escalation to a person, because the failure that costs you is the one nobody noticed.
Two things you can check
Big Berri Limited is registered in England and Wales, company number 16562429, and registered with the Information Commissioner's Office under reference ZC119995. Both are public registers. Look us up rather than taking our word for it.
Ready to Build Your App?
From first wireframe to App Store launch — we build mobile apps that users love and businesses depend on.
Book a Free Discovery Call