The verdict in three sentences
A custom B2B e-commerce platform in London costs, in 2026, between 40,000 and 120,000 EUR depending on pricing-rule and integration complexity, delivered in 5 to 8 months. The financial upside comes not from pure online sales but from lower sales-admin cost (30-50%) and a higher average order value (10-20%) through self-service reordering. If your pricing is standard, an off-the-shelf platform from 2,300 EUR/month is enough; custom pays off as soon as your prices, credit terms and workflows are specific.
What B2B e-commerce must cover (and B2C does not)
A B2B portal is not a consumer store with a corporate logo. It handles per-customer pricing, multi-user accounts (buyer, approver, accountant), credit lines and payment terms, volume discount tiers, and quick ordering by SKU or CSV import. That foundation saves your pro customers time and unclogs your sales-admin team.
| B2B feature | Custom build | Shopify Plus B2B |
|---|---|---|
| Per-customer / per-group pricing | Unlimited, complex rules | Company-level catalogs and prices |
| Multi-user accounts + roles | Custom (approvers, budgets) | Standard (role limits) |
| Credit / payment terms | Native, ERP-linked | Via app or limited net terms |
| Quick order / CSV reorder | Custom | Available |
| Deep ERP integration | Full | API but integration effort |
| Entry cost | 40,000-120,000 EUR | From 2,300 EUR/month + integration |
Detailed budget for a custom build in London
Cost is driven mostly by the number of business rules and the depth of ERP integration. Here is a 2026 order of magnitude for a distributor or manufacturer.
| Item | 2026 range (EUR) | Note |
|---|---|---|
| Scoping + B2B UX/UI | 5,000 - 12,000 | Pro buyer journey, mockups |
| Catalog + pricing engine | 10,000 - 30,000 | Tiers, discounts, customer prices |
| Accounts + roles + credit | 8,000 - 20,000 | Multi-user, approval |
| ERP / stock integration | 10,000 - 35,000 | Prices, stock, orders, customers |
| Quick order + reorder | 4,000 - 12,000 | CSV import, lists, favourites |
| QA + go-live | 5,000 - 15,000 | Testing, training, cutover |
| Total | 40,000 - 120,000 | Depending on scope |
Add maintenance at 10-15%/year of build cost and hosting of 100 to 400 EUR/month depending on traffic.
Mini case study
Thomas is sales director of an industrial supplies distributor in London: 320 pro customers, 6 sales-admin staff keying 90 orders/day received by email and phone. He invests 68,000 EUR in a custom portal. After 6 months, 55% of orders come in online. Sales-admin frees roughly 2.5 FTE redeployed to customer advice; at 42,000 EUR loaded cost/year per role, that is ~105,000 EUR/year. Average order rises 12% through suggested reordering. Payback in under 9 months.
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What does a B2B e-commerce platform really cost in London in 2026?
Expect 40,000 to 120,000 EUR for custom, or from 2,300 EUR/month for Shopify Plus B2B plus 15,000 to 40,000 EUR of integration. The gap depends on pricing and ERP complexity.
How long to deliver?
Between 5 and 8 months for a full custom build. An MVP focused on quick order and customer pricing can ship in 3 to 4 months.
Is custom worth it versus SaaS?
Yes, as soon as your pricing rules, credit terms or integrations are specific: you avoid a platform subscription and the transaction fees that bite at high volume.
What concrete gain on sales-admin?
A well-designed portal absorbs 40-60% of recurring orders, cutting sales-admin workload by 30-50% and sharply reducing keying errors.
Must everything be built at once?
No. Start with the highest-ROI features (customer pricing, quick order, accounts) then add credit terms, analytics and PWA in iterations.
Let's scope your project. Describe your catalog, pricing rules and ERP: we will size a right-scoped B2B portal, budget 40,000-120,000 EUR. 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.