If your office internet drags at the worst possible moments, or you're moving premises and weighing your options, here's the short answer: business broadband is cheaper, shared with other users and quick to install, while a leased line is a dedicated connection that costs more but gives you guaranteed speeds, matching upload and download, and a contract that genuinely commits the provider to fixing faults fast. Which is better depends far less on the headline speed than on what an hour offline actually costs you.
Here's how the two compare in practice, and how to decide without overpaying or under-buying.
What business broadband actually is
Most UK offices run on the same full-fibre (FTTP) or part-fibre (FTTC) technology you'd find at home, just on a business tariff with priority support. It's delivered over Openreach's shared network, and two things follow from that.
It's contended (shared)
Your connection is shared with other premises in your area. When the local network is busy - usually mid-morning and straight after lunch - everyone's speed dips. You're buying a maximum, not a guarantee. A line sold as 900 Mbps might give you 900 at 7am and noticeably less when the whole street is on a video call.
It's usually asymmetric
Download speed is much higher than upload. That's fine for browsing and streaming, but it bites the moment your team leans on the cloud: backing up to Microsoft 365, sending large files, running Teams calls, or hosting anything customers connect to. A connection advertised as 900 Mbps down might only offer 100-115 Mbps up.
For a small team that mostly emails, browses and runs a few cloud apps, good full-fibre business broadband is often perfectly adequate, and you can be live in roughly two weeks.
What a leased line gives you that broadband can't
A leased line is a dedicated fibre connection that runs from your building straight back to the provider's network. Nobody else uses it. That changes three things that matter.
Uncontended bandwidth. You get the full speed you pay for, all day, every day. 9am Monday is no different from 3am Sunday.
Symmetric speeds. Upload matches download. A 200 Mbps leased line is 200 Mbps up and 200 Mbps down, which is what makes cloud-heavy work feel instant rather than sluggish.
A real service guarantee. This is the part most businesses underrate, and it's covered below.
Leased lines are also easy to scale. Many are delivered on a higher-capacity bearer than you initially use, so you can step up the speed with a phone call rather than a fresh installation.
The bit that really separates them: the SLA
Speed gets all the attention, but the Service Level Agreement (SLA) is where leased lines earn their cost. Broadband is sold as a best-effort service. If it goes down, the provider will aim to fix it, but there's no contractual deadline. In practice a broadband fault can take anywhere from a few hours to two or three working days, and you have little leverage while you wait.
A leased line comes with hard commitments, typically:
Guaranteed uptime of 99.9% or higher, with many providers quoting 99.95% or above.
A target fix time measured in hours - a four-hour fix SLA is common - rather than days.
Service credits if the provider misses those targets, so the guarantee has teeth.
That difference is the whole decision in miniature. You're not just buying faster internet; you're buying a promise about how quickly you'll be back online when something breaks, because eventually something will.
The real question: what does downtime cost you?
Set the speed numbers aside for a moment and do a quick sum. If your business stops when the internet stops, work out roughly what one hour offline costs in lost orders, idle wages and missed calls.
A simple way to frame it: take the number of people who can't work, multiply by their loaded hourly cost, then add anything you'd lose in sales or bookings. A 15-person office where everyone is paid an average of £25 an hour is burning £375 an hour in wages alone before you count a single lost order. Lose half a day twice a year to a best-effort broadband fault and you're well into four figures, on top of the stress and the apologies to customers.
Once you have that figure, the leased line maths usually makes itself. If a connection that's down for hours costs you thousands, paying a few hundred pounds a month more for a guaranteed four-hour fix isn't an extravagance, it's insurance. If your team can comfortably pick up the phone, work offline for an afternoon and catch up later, that guarantee is worth far less and broadband is the sensible call.
Cost and lead time: plan ahead
Two practical realities catch businesses out, especially around an office move.
Cost. As a rough 2026 guide, business full-fibre broadband sits around £40-150 a month plus VAT, with installation in the low hundreds. A leased line is typically £200-1,000+ a month depending on speed, with one-off installation from around £1,500 and considerably more if Openreach has to carry out civil works - digging up pavements or running new fibre to your building.
Lead time. Broadband is usually live in 10-15 working days. A leased line commonly takes 60-90 working days, sometimes longer where civils or a wayleave (the landlord's permission to install) are involved. If you're moving offices, order the line the moment you've signed the lease, not when you've collected the keys. Leaving it late is the single most common reason a new office opens without proper internet.
The hybrid most growing SMEs land on
You don't have to pick one and live with the trade-off. A popular and sensible setup is a leased line as the primary connection with a separate broadband or 4G/5G line as automatic failover. If the leased line ever drops, a router with dual connectivity switches over in seconds and your team keeps working, often without noticing.
This matters more than it used to. With the PSTN big switch-off on 31 January 2027 moving phones, card machines, alarms and door entry onto internet-based services, your connection is no longer just for email. It increasingly carries the things that used to run on a separate phone line, so a second route to the internet stops one fault taking out your whole front of house.
How to right-size your connection
When we help a Berkshire business choose, we weigh four things rather than just chasing the biggest number.
Headcount and growth. A handful of people browsing and emailing have very different needs from 30 staff on constant video calls. Size for where you'll be in two years, not just today.
Cloud reliance. If your phones, files, line-of-business apps and backups all live in the cloud, the internet is your office, and symmetric, guaranteed bandwidth stops being a luxury.
Upload demands. Large file transfers, video editing, offsite CCTV, hosted services and lots of Teams calls all lean on upload - exactly where broadband is weakest.
Tolerance for downtime. Be honest about what happens at hour one and hour four of an outage. That answer, more than anything, points you to broadband, a leased line, or a hybrid.
The bottom line
Business broadband is the right answer for plenty of small offices: affordable, fast enough and quick to install. A leased line earns its higher price when downtime genuinely costs you money, when your work is upload-heavy or cloud-first, or when you simply can't afford to be the business that's offline for two days waiting on a best-effort repair.
If you're not sure which side of that line you fall on, or you've an office move coming up and want the connectivity ordered early, our team is happy to look at your usage, your floor plan and your tolerance for downtime, and tell you honestly what's worth paying for.