SaaS MVP development in the UK: scope, cost and timeline

A SaaS MVP built properly by a UK agency usually costs between £7,000 and £20,000 ex VAT and takes 10 to 16 weeks from first workshop to paying users. At WE-DEV that buys you sign-up and login, Stripe subscriptions, one core workflow done well, an admin area and a production setup you won’t have to throw away. Anything much cheaper is usually a prototype; anything much dearer is usually a version two in disguise. The rest of this guide explains what goes into that range, what to leave out, and how to keep the first release small enough to ship.

What “MVP” should mean for a SaaS product

The phrase has been stretched until it means almost nothing. Some founders use it for a clickable Figma file, others for a product with eight user roles and a mobile app. For software you plan to charge for, we use a narrow definition: the smallest product a stranger can sign up to, pay for and get real value from without you on the phone holding their hand.

That definition does two useful things. It rules out the demo that only works when you drive it, and it rules out the feature list that grew in a spreadsheet over six months. If a feature doesn’t help a new customer reach the moment where they think “this saves me time”, it waits.

The parts every SaaS MVP needs

• Accounts: sign-up, email verification, password reset, and ideally sign-in with Google or Microsoft if your buyers live in those tools.
• Billing: Stripe subscriptions with a free trial or a first-month offer, card updates, cancellations and invoices with your VAT number on them.
• Multi-tenancy: each customer’s data kept apart, usually as “workspaces” or “organisations” with an owner who can invite colleagues.
• The core workflow: the one job your product exists to do, built carefully, with sensible empty states and error messages.
• An admin area for you: see customers, impersonate a user to debug a problem, issue refunds, switch features on per account.
• Transactional email, error monitoring, backups and a privacy policy that matches what the software actually does.

That list looks short. In our experience it is about 60 % of the build effort on a typical first release, and it’s the part founders most often underestimate because none of it feels like “the product”.

What to leave out of version one

• Native mobile apps. A responsive web app works on phones; build apps when usage data says people want them.
• Granular roles and permissions. Owner and member is enough for most B2B products at launch.
• Single sign-on via SAML. Add it when an enterprise customer asks and is prepared to pay for the tier that includes it.
• More than one integration. Pick the one your first customers can’t live without (Xero, HubSpot, Google Calendar) and do it well.
• Custom reporting builders. Ship three fixed reports and an export to CSV.
• Usage-based pricing, unless your whole business model depends on it. Flat monthly tiers are far simpler to build, test and explain.

What a SaaS MVP costs in the UK

UK agency day rates for this kind of work typically run from around £450 to £900 a day, and freelance rates vary even more. Our Custom Web Development rate is £60 an hour, with volume discounts on prepaid hours (10 h 5 %, 15 h 10 %, 20 h 15 %, 50 h 20 %, 100 h 25 %), and hours never expire. All figures below exclude VAT at 20 %.

The prototype row uses our UI/UX Design rate of £55 an hour; the build rows use the 25 % discount that applies to blocks of 100 hours or more at £60.

A worked example

Say you’re a former logistics manager in Leeds with an idea for a delivery-slot booking tool for small warehouses. After a discovery workshop the scope comes to roughly 300 hours of development plus 30 hours of interface design.

• Design: 30 h × £55 = £1,650, less 15 % (20-hour band) = £1,402.50.
• Development: 300 h × £60 = £18,000, less 25 % (100-hour band) = £13,500.
• Total: £14,902.50 + VAT £2,980.50 = £17,883 including VAT.

You can pay in full or put down a 50 % deposit, and because the hours don’t expire, any you don’t use stay on account for the changes that always follow the first month of real users. If you’re VAT-registered, you reclaim the £2,980.50, so the real cost to the business is the ex-VAT figure.

Running costs after launch

Building it is the larger cheque, but budget for these every month from day one:

For most MVPs that adds up to somewhere between £350 and £1,000 a month in the first year, most of it in development time for fixes and small improvements.

A realistic timeline

Sixteen weeks sounds long when you’re excited. It’s quick for software that strangers will pay for. Here is how a typical Standard MVP breaks down with us:

1. Discovery (1–2 weeks): workshops, user journeys, a written scope ranked by value, and a fixed list of what’s out.
2. Design (2–3 weeks): wireframes, then high-fidelity screens for the core workflow, tested with three to five target users if you can find them.
3. Build (6–10 weeks): fortnightly releases to a staging site you can click around, with a short call after each one.
4. Private beta (2–4 weeks): ten to thirty friendly users on the real system, free or discounted, with a feedback channel.
5. Launch: billing switched to live, onboarding emails on, and a support rota for the first fortnight.

The phase founders try to cut is the beta. Don’t. It is the cheapest month of learning you’ll ever buy, and every product we’ve seen skip it has spent the saved time later fixing problems in front of paying customers.

Choosing the tech stack

For most B2B SaaS we build in Laravel (PHP) with a Vue or React front end and a MySQL or PostgreSQL database. It’s mature, there are thousands of UK developers who can pick it up if you ever move on from us, and it handles accounts, queues, billing and email without exotic dependencies. When the product is real-time or mobile-first, we use Node with Firebase, and Flutter if a companion app for iOS and Android is part of the plan.

Our opinion: choose boring technology for an MVP. The stack that wins on Hacker News this month will not matter to your first fifty customers, but the ability to hire a second developer in Manchester or Bristol without a three-month search will. Hosting on a mainstream cloud provider behind Cloudflare is plenty until you have thousands of active users.

Single database or one per customer?

Nearly every MVP should use one shared database with a tenant ID on each record. Separate databases per customer make sense for some regulated sectors or for enterprise buyers who demand it, but they multiply the work on migrations, backups and reporting. If you think you’ll need it later, tell us at the start and we’ll structure the code so the switch is possible without a rewrite.

UK-specific things to sort before launch

• UK GDPR: you’re a data controller for your own customers’ details and usually a processor for the data they put into your product. You’ll need a data processing agreement your B2B customers can sign, and the ICO’s guidance explains what goes in one.
• ICO registration: most UK businesses that process personal data must pay the ICO data protection fee. The lowest tier is modest, but check the current amount on the ICO website.
• VAT: B2B sales to VAT-registered UK customers are standard-rated; selling digital services to consumers abroad brings in their local VAT rules. Stripe Tax can calculate it, and your accountant should confirm the setup.
• Intellectual property: your contract should assign the code to your company. With us, once the work is paid for, the code, database and documentation are yours, in a repository you control.
• Funding: if you’re raising from angels, HMRC’s SEIS and EIS schemes give investors income tax relief on qualifying shares. Software development can also qualify for R&D tax relief under the merged scheme that applies to most accounting periods from April 2024, but only where the work resolves genuine technological uncertainty. A standard subscription app built on well-known tools usually doesn’t. Get advice from a specialist before you count on it.

Where SaaS MVPs go wrong

We’ve inherited enough half-built products to see the same patterns. Most of them have nothing to do with code quality.

• The scope grows during the build. A new idea every week feels like progress and adds a month every quarter. Keep a “version two” list and be ruthless about it.
• Billing is left until the end. Stripe subscriptions touch sign-up, permissions and emails. Build them in the first sprint, not the last.
• No one owns onboarding. The first ten minutes after sign-up decide whether a trial converts. Write the welcome emails and design the empty states as carefully as the main feature.
• Too much is built before anyone pays. If you can, sell the product to three customers before the build starts, even at a founder discount. Nothing sharpens a scope like a customer waiting for it.
• The handover is an afterthought. Ask for documentation, a deployment guide and access to every account from week one, not at the end.

KDMasterKey is a fair example of the shape we like. We built web-based keyword-analysis software for self-publishers, with its own users, accounts and data, plus a companion app. It started with the job its users needed most and grew from there.

Pre-build checklist

Before you ask anyone for a quote, write down answers to these. A good agency will help you refine them, but arriving with a first draft saves a week of discovery.

• Who is the first customer, by job title and company size?
• What do they do today instead of using your product, and what does that cost them?
• What is the single workflow the MVP must do well?
• How will you charge: per user, per account, by tier?
• Which one integration matters most?
• What is your budget ceiling, including three months of running costs and fixes?
• Is there a date that matters, such as a trade show, a funding round or a pilot customer?
• Who on your side will test each release and make decisions within a day or two?

Our recommendation

• If you haven’t spoken to ten potential customers yet, don’t build software. Spend £1,000–£2,000 on a clickable prototype and test the idea first.
• If you have a validated problem and a modest budget, scope a Lean MVP at 150–200 hours and plan to spend the same again over the following six months.
• If you already have paying pilots or a funded round, go for a Standard MVP with one integration and a proper beta, and budget for a developer on retainer after launch.
• If your product handles health, financial or children’s data, add a security review and penetration test before launch rather than after.

Our team is based in St Albans and works with founders across the UK, from London to Edinburgh, mostly remotely with in-person workshops where they help. If you’d like a scope and estimate for your idea, start with our custom software development page, book prepaid hours on hire us, or talk to us about UX design for the prototype stage. For app-specific figures, read how much an app costs to build in the UK, and before launch, run through our software testing checklist.

Photo: Kaleidico via Unsplash