I just check uSwitch and BT is not even listed as one that can be compared directly.

Having said that I jut compared the different providers both on uswitch.com and thinkbroadband.com, It appears the cheapest is actually O2 with £90 for 12 contract for 8Mb unlimited transfer (**Subject to providers fair usage policy). Compared with your BT Option 1 will set you back £270 by the end of 18 month contract.

In my opinion I rather pay that £90 to O2 for 12 months and by end of it I am sure price will drop even more so I can switch to some other contract and save even more.

As rule of thumb, I found that both broadband and mobile phone contract price drops every 12 months, or at least you get a better deal for your money. Knowing that I’d never recommend anyone sign-up to a 18 months contract, as it ties you up the provider for additional 6 months where you can effectively get a better deal and also save money.