The two circuits that matter for UK businesses in 2026 are full-fibre to the premises (FTTP) and ethernet leased lines. They look similar on a quote — both give you internet access at speeds up to 1 Gbps or higher — but they are very different products with very different price tags and use cases.
This guide explains, in plain English, what each is, what they actually cost, and — the important bit — when each is the right answer for your business.
What FTTP actually is
FTTP (Fibre To The Premises) is a fibre-optic cable run from the exchange all the way to your building. It is a "contended" service — meaning the underlying capacity between your building and your carrier's core is shared with other users on the same fibre. You get advertised speeds up to 1 Gbps download and 200 Mbps upload; the reality on a busy business estate at 3pm on a Tuesday is usually around 70–90% of that.
FTTP comes with next-business-day fault repair (business-grade — the residential version has slower SLAs) and typically includes a static IP address. Business FTTP in 2026 costs £30–£90 per month depending on speed, carrier and contract term.
What a leased line actually is
An ethernet leased line is a dedicated, uncontended fibre circuit from your building to your carrier's core network. "Uncontended" means the full bandwidth is yours all the time — nobody else shares it. Speeds are symmetric (same up as down), typically from 100 Mbps to 10 Gbps.
A leased line comes with a real service-level agreement: 99.99% availability, typically a 4-hour or 5-hour fix time, and a business-continuity obligation on your carrier that FTTP does not include. Leased lines in 2026 cost £250–£1,200+ per month depending on speed, location and cable route, plus a one-off installation charge that can range from zero (if a fibre is already close by) to several thousand pounds (if new fibre has to be laid).
Which one do you actually need?
Here is the honest answer: for most UK small businesses under 40 users, business-grade FTTP with 4G/5G failover is the right choice. It is fast enough, resilient enough, and about a quarter the cost of a leased line. The extra money you would spend on a leased line is better spent on a proper managed router, a phone system and 4G backup.
For medium-sized businesses (40–150 users), it depends on what you actually run over the connection. If it is mostly email, browsing, Microsoft 365 and cloud CRM — FTTP is probably fine. If it is a heavy contact-centre, large file transfers to and from the cloud, 40+ concurrent VoIP calls at peak, or anything where downtime means real revenue loss — a leased line, or FTTP+leased-line backup, becomes the right answer.
For any business where the connection is business-critical — contact centres, manufacturing, professional-services HQs, hospitality with EPOS — you want a leased line. And for anything where a full-day outage means five figures of lost revenue, you want a leased line PLUS a diverse-route secondary circuit from a different carrier.
The scenarios in detail
- 5-person accountancy practice, cloud-based, one small office — FTTP with 4G backup. About £70/month.
- 20-person marketing agency, heavy cloud use, mixed office and home — FTTP 1 Gbps with 4G backup. About £120/month.
- 80-person recruitment firm with 60 concurrent calls, HubSpot, cloud everything — FTTP is on the edge; a 200 Mbps leased line is safer. About £450/month.
- 30-seat contact centre with SLA-driven inbound calls — leased line, non-negotiable. About £500–£700/month depending on speed.
- Multi-site retail chain with EPOS and card payments — FTTP at each shop with 4G failover, SD-WAN overlay for site-to-site.
- Manufacturing plant, 24-hour operations, ERP in the cloud — two leased lines from two carriers on diverse routes, plus 5G tertiary.
What "diverse routing" actually means (and why it matters)
A leased line is dedicated on the last mile, but every fibre eventually converges at an exchange or aggregation point. If a JCB cuts your carrier's trunk fibre outside your building, both your primary and secondary leased lines from that carrier will go down together. That is why diverse routing matters — two leased lines from two different carriers, on two different physical cable routes.
Not every business needs it. But if your business genuinely cannot lose a day, a properly designed dual-carrier setup with automatic failover is what "business continuity" actually looks like — not a phone number for a helpdesk in Bangalore.
FTTP with 4G/5G failover — the modern SME sweet spot
For most UK SMEs in 2026, the smart move is business-grade FTTP with a 4G or 5G failover built into the router. If the FTTP drops, the router falls over to a mobile SIM within seconds and keeps critical traffic (voice, card payments, VPN) flowing. When the FTTP recovers, it fails back automatically. Nobody notices except in the network monitoring.
A business FTTP + 4G failover setup in 2026 costs about £80–£140 per month including managed router — a fraction of a leased line, with most of the resilience.
The questions to ask before you quote
We can run an availability check at your postcode across every carrier — BT, Openreach, Virgin Media O2, CityFibre and altnets — and tell you what is actually deliverable, at what price, before you commit to anything.
Atom IP delivers Broadband & Leased Lines across the UK. Book a free technology review and we’ll come back with practical, jargon-free findings.
