The verdict in three sentences
A B2B SaaS MVP in London costs between £60,000 and £120,000 in 2026 for 12 weeks of development, i.e. 15 to 30% of a £400,000 pre-seed round. The goal is not to build everything but to ship one core feature with Stripe Billing subscriptions to 5 paying pilot customers. A small agency team (day rate £650 to £900) lowers the timeline risk, freelancers (day rate £500 to £700) lower the bill but need more steering from the founder.
What goes into a 12-week B2B SaaS MVP
A credible B2B MVP for pilot customers includes authentication with team management, the core feature that solves the problem, a minimal dashboard, recurring billing and security basics. Everything else (multiple integrations, mobile app, marketplace, advanced reporting) waits for pilot feedback.
| Building block | MVP scope | Person-days | Indicative budget (£, day rate £800) |
|---|---|---|---|
| Scoping and design | Workshops, user flows, Figma mock-ups | 8 to 12 | 6,400 to 9,600 |
| Authentication and teams | Login, invitations, roles, Google SSO | 6 to 10 | 4,800 to 8,000 |
| Core feature | The business flow that justifies the subscription | 25 to 60 | 20,000 to 48,000 |
| Dashboard | Key metrics, CSV exports | 6 to 12 | 4,800 to 9,600 |
| Stripe Billing | Plans, free trial, invoices, customer portal | 4 to 8 | 3,200 to 6,400 |
| Infrastructure and security | UK/EU hosting, backups, logs, UK GDPR | 5 to 10 | 4,000 to 8,000 |
| Testing and go-live | Acceptance, monitoring, pilot onboarding | 6 to 12 | 4,800 to 9,600 |
With 60 to 125 person-days, the range lands between £48,000 and £100,000 at the average agency rate, and can reach £120,000 when the core feature involves AI or an ERP integration.
Agency, freelancers or in-house CTO: the comparison
| Criterion | Agency (£650 to £900/day) | Freelancers (£500 to £700/day) | In-house CTO plus 1 developer |
|---|---|---|---|
| 12-week MVP budget | £60,000 to £120,000 | £45,000 to £85,000 | £55,000 to £70,000 loaded over 3 months, plus hiring |
| Time to start | 2 weeks | 2 to 4 weeks | 3 to 6 months of hiring |
| Team | PM, designer, 2 developers, QA | 2 developers, design separate | 2 people |
| Overrun risk | Low with fixed price | Medium, founder-managed | High at the start |
| Code ownership | Assigned to client | Assigned to client | In-house |
| Best fit | Launch fast without a CTO | Technical founder | After product-market fit |
Our 2026 recommendation: agency or a freelancer pair for the MVP, hire the CTO once the 5 pilots convert into paying customers.
Recurring budget after launch
| Item | Monthly cost 2026 |
|---|---|
| Hosting (Vercel, AWS London or GCP) | £45 to £130 |
| Managed database | £20 to £90 |
| Transactional email and monitoring | £20 to £70 |
| Tools (Sentry, analytics, support) | £45 to £60 |
| Total infrastructure | £130 to £350 |
| Stripe Billing | 0.7% of billed volume, plus card fees of 1.5% + 20p for UK cards |
| Agency maintenance and evolution | £1,500 to £4,000 |
Mini case study
James, founder of a London B2B startup automating ESG compliance for SMEs, has raised £400,000 in pre-seed. He hands the MVP to an agency for a fixed £82,000, 12 weeks. Infrastructure: £220 a month. His 5 pilots sign at £450 a month, i.e. £2,250 MRR in month 4. If he reaches 25 customers by month 12, MRR rises to £11,250 and ARR to £135,000, enough to pitch a seed round with a product build cost of just 20.5% of his raise.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
FAQ
What budget for a B2B SaaS MVP in London in 2026?
Between £60,000 and £120,000 for 12 weeks, depending on the complexity of the core feature. The observed average is around £80,000 for an agency team.
Is twelve weeks realistic?
Yes if scope is limited to one core feature and the founder approves mock-ups within 5 days. Each feature added mid-project costs 1 to 2 weeks.
Should Stripe Billing be in the MVP?
Yes, charging pilots from month one validates value. Integration costs £3,200 to £6,400 and Stripe takes 0.7% of billed volume.
Fixed price or time and materials?
Fixed price protects your pre-seed cash: the price is locked for a written scope. Time and materials suits the post-MVP phase, iterating sprint by sprint.
Who owns the code?
You do, through an IP assignment clause in the contract. Also require access to the Git repository from week one.
Let's scope your project. Send us your core feature, your pilots and your target date: we will quote a fixed-price MVP between £60,000 and £120,000, delivered in 12 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
