avoid talktalk, sky and bt like the plague all can have severe congestion at peak times and as ppl have said talktalk and sky have beyond retarded customer services
Vigin does have some ping issues with wow, had a few guildies have probs with them.
Personally i would go with BE (bethere) part of the O2 group, been with these guys for years now and it is by far the very best isp ive ever had / seen
all the maintenance is done at like 3am in the morning to avoid disruptions and they always send you a txt message and email a good few days prior to warn you.
They also have fantastic customer support, they also seem to know wtf there talking about if you call em (not some pakistani / indian) reading from a script that doesnt know his asshole from his elbow lol. give em a look
www.bethere.co.uk