In comparison, Telewest and Pipex ADSL are not too bad, although anythign that has to rely on a BT network can get FUBAR (f**ked up beyond redemption) oft times.
Also, since broad band networks have an exclusivity licesne, eg. IN North london, you may only get Telewest, and not NTL, whereas in Swindon you only get NTL...so your choice is always limited between either cable company NTL/Telewest vs a BT pipeline (BT broandband, Freeserve, F9, Pipex, blah blah)
Alternatively...there is the great fish eye in the sky connection, i.e Sattelite Broadband connection. As I'm with telewest for past 3 years..havent had the guts to go changing things...