Stay the hell away from BT - BT Internet are totally legally separate from the people who provide the most of the guts of the internet service, so the argument that sometimes gets bought up, of "it's all BT so if it goes wrong they can fix it quicker" is complete bollocks.

If she's got an O2 mobile then there's a cheap deal that O2 broadband do (and is actually provided by "Be" who are good)