I'm currently with EasyNet, but that is only because when I got ADSL 2 years ago I wanted the 1Mb business service and at that point EasyNet were the cheapest for 1Mb.

I am thinking of downgrading my service to the consumer 512k service and switching to Andrews & Arnold. This will save me 90 quid a month, most of which I can then spend on a colo box in telehouse or where ever.

A&A have been putting in line monitoring that puts all the other ISPs to shame, they are spotting and reporting faults to BT before the users even notice there is a problem.

The other ISP that appears to know what it is doing with ADSL is PlusNet, they are also probably about the cheapest.