I used to work for BT and sell their internet lease lines that Mike refers to.

I now have no love for BT, but their BTnet (internet lease line) is best of breed.
With any internet lease line you throw off the limitations of an ADSL (broadband) and get true performance for your money.
Yes it cost 10 times as much as broadband, but you get 100 times the performance.
You can compare the speeds a 24Mb broadband will still be slower than a 2Mb lease line.
I am not going to bore you with why, but a more important benefit having an Internet lease line gives is reliability. You broadband may work now but it’s a commodity product, and fixes are best endeavours by ISP's. Broadband is now an essential part of any businesses communication with their customers.
As soon as a fault occurs you stand to lose money, not just for companies that you trade on line, but every business. Without an internet connection you can't reply to customer emails, take orders from your website and if you hosting your own website then that disappears! and customer could think you have stopped trading and try a competitor!

With an Internet leased line you will have a robust SLA. Service Level Agreement and if it's a BTnet then you get 24/7, 365 cover and a 4 hour response to fix it. In November 2009 they were running at a 2hr fix nationally. Its part of what you’re paying for.
Yes it cost around £5k+ per year, but what is the cost of one day’s loss of business?