When I was checking for a new broadband deal, I was a bit suprised how far BT has become competitive in the last year. About a year and a half back,
I did have an impression that BT are always expensive than others, but things seem to have changed for the better. Now their packages are very competitive in pricing, features and bandwidth limits. BT is my current ISP and I have no complaints whatsoever (so far!)
Their current offers can be
compared on the BT Broadband page of this site.
Another thing to note is that the quality of hardware like wireless routers and modems you get free with their packages is also getting better.