Full fibre, leased line or broadband: which does your business need?

Choosing business internet has a dirty secret: most of the comparison articles are written by companies that only sell one of the options. Leased-line resellers write about how broadband is a false economy; broadband providers write about how leased lines are overkill. This guide is written for UK business owners and office managers who want the honest picture. We sell all of the options below, which is precisely why we do not need any single one of them to win. Every factual claim is backed by the sources at the end, most of them Ofcom, Openreach and BT Wholesale primary documents.

The short version.

• There are three ways into a building: copper-based broadband (being retired), full fibre (excellent and now widely available), and a leased line (dedicated, symmetrical, guaranteed, and priced accordingly).
• The real difference is not raw speed. It is shared versus dedicated, upload versus download, and what happens when it breaks.
• The map has changed fast: full fibre reached 82% of UK homes by January 2026, and Openreach is actively withdrawing copper broadband from sale where fibre is built.
• Leased lines take weeks to months to install, so the right time to order one is before you need it, not after.
• And sometimes the connection is innocent: a surprising amount of “slow internet” is actually the network inside the building.

The three ways into a building.

Option	What it really is	Speed, in practice
Copper broadband (ADSL, FTTC)	Internet over telephone-era copper, in whole or in part	ADSL up to 24 Mbit/s, FTTC normally up to 80 Mbit/s, both degrading with distance from the exchange or cabinet
Full fibre (FTTP)	Fibre all the way to your premises, capacity shared with neighbouring premises	Gigabit-capable, speed unaffected by distance, uploads usually slower than downloads
Leased line	Your own dedicated fibre circuit, built to order for your address	The speed you buy in both directions, uncontended, guaranteed by contract

Those speed characterisations are Ofcom’s own, not marketing. Two clarifications worth having. First, “full fibre” and “leased line” both arrive on fibre; the difference is that FTTP shares network capacity between roughly 30 and 60 premises, while a leased line is yours alone. Second, copper broadband is on its way out regardless of preference: where an exchange reaches 75% full-fibre coverage, Openreach stops selling copper services, and by early 2026 around 12.5 million premises across 1,281 exchanges were already under that stop-sell, with more tranches following. If your business is still on FTTC or ADSL, the question is not whether you move, but when and to what. That story connects to the wider 2027 analogue switch-off, which retires the phone network the oldest broadband rides on.

What the brochures gloss over.

Shared versus dedicated. Full fibre is superb for most businesses, and we say that as a company that profits more when you buy the expensive option. But it is a shared medium, sized for the statistical likelihood that your neighbours are not all busy at once. A leased line removes the neighbours from the equation. Whether that matters depends entirely on what your business does when the connection wobbles at 2pm on invoice day.

Upload versus download. Broadband products, including most FTTP, give you far more download than upload. That made sense when offices consumed the internet. A modern office produces as much as it consumes: video calls, cloud backups, files syncing to SharePoint or Drive. If your business has moved to the cloud, upload is the speed you actually feel, and it is the number the headline never mentions. Leased lines are symmetrical: the same speed both ways.

What happens when it breaks. This is the real product difference. Business broadband from providers signed up to Ofcom’s Business Broadband Code of Practice comes with a minimum guaranteed speed at the point of sale and a right to exit without penalty if a speed problem cannot be fixed within 30 days. That is genuine consumer protection, but read it again from the perspective of a business that is offline: your remedy is leaving. A leased line’s remedy is repair: the regulated Openreach Ethernet service level is a 5-hour fix, 24 hours a day, 365 days a year, with at least 94% of faults required to meet it. Broadband is a service you subscribe to; a leased line is a service level you can hold someone to.

The map is changing under your feet.

Whatever you concluded the last time you looked at connectivity, the ground has moved:

• Full fibre reached 82% of UK homes (24.9 million premises) by January 2026, per Ofcom’s Spring 2026 update, up 1.2 million homes in six months.
• The business picture: 78% of UK SMEs had full-fibre access as of July 2025 (Connected Nations 2025), though Ofcom notes part of that year’s jump reflects better data reporting rather than purely new build.
• Openreach’s own network passed 20 million premises in September 2025 and is targeting 25 million by the end of 2026, alongside the independent networks building in parallel.
• One quirk worth knowing: Ofcom’s coverage statistics do not include leased lines, which are built to order. An address that shows as poorly served on a coverage checker can very often still have a dedicated circuit delivered to it.

The practical consequence: if your last connectivity decision was made even two years ago, the options at your address have probably changed. Check before you renew, not after.

How to choose.

Four questions, in order of importance:

1. What does an hour offline actually cost? Count it properly: staff paid to wait, card payments missed, calls that went to a competitor, the cloud systems you now depend on. If the number is small, congratulations: buy good full fibre and spend the savings elsewhere. If the number is frightening, the leased line’s fix-time guarantee is what you are really buying.
2. How much do you send, not just receive? Count the video calls, the cloud backup window, the file syncing. Upload-heavy businesses feel asymmetric connections first and worst.
3. How long can you wait? Full fibre installs are typically quick. A leased line is built to order: BT Wholesale quotes a standard lead time of 33 working days for the fibre access leg, the regulated average for Ethernet circuits runs at 38 to 40 working days, and every quote is subject to survey, which can extend it. Moving premises or opening a site? Order the connectivity the day the lease is signed, not the week before opening.
4. Does anything stop you having both? Nothing. A common pattern for businesses that care about uptime but not enough to justify a leased line: good full fibre as the main line, a second connection over a different path (often 4G or 5G) that takes over automatically when the first fails. In our experience that pairing covers most real-world failures for a fraction of a leased line’s cost, and we will say so when it is the right answer for you.

On cost, we deliberately print no prices: they vary by address, speed and term, and any figure would date this guide within months. The structure is this: a leased line costs several times more than broadband because you are paying for exclusivity and the repair guarantee; installations can attract construction charges where new ducting is needed (a survey tells you before you commit); and contracts run longer. If a quote surprises you in either direction, ask what service level is attached to it. That is usually where the difference lives.

Before you blame the connection.

A diagnostic that connectivity articles rarely include, because their authors sell connectivity: a significant share of “the internet is slow” complaints we investigate turn out to be nothing to do with the internet. The line arrives at the building at full speed, then loses it inside: a consumer-grade router doing a business’s job, WiFi access points from a previous decade, one access point asked to cover three floors, or cabling installed when the building had half the staff.

The tell is the pattern. If things are slow everywhere including on wired desktops, suspect the connection. If they are slow in the far meeting room, fine near the router, and worse when the office is full, the connection is probably innocent and the network inside the building is the real project. Upgrading the line while keeping the old network is the most common way businesses spend money on this problem without fixing it. A proper assessment looks at both ends before recommending either.

The bottom line.

Most UK small businesses in 2026 are best served by good full fibre, and it is available to more of them every month. Businesses where downtime is genuinely expensive should price the leased line against what an outage costs, not against the broadband bill, and order it earlier than feels necessary. Anyone still on copper broadband should treat their next renewal as the moment to move, because the choice is being made for them tranche by tranche. And before any of it, make sure the building’s own network is not the real bottleneck, because the fastest line in Britain cannot fix ageing WiFi.