The conclusion of my research was thus (looking at 512kb connections)
Tiscali
monthly:
19.99 (50 hrs) /
24.99 (unlimited)
setup: 25 / FREE
modem: FREE
extras: NA
Eclipse
monthly:
20.38
setup: 50
modem: 34
extras: 20mb webspace
PlusNet
monthly:
14.99 (1GB then 2.50 per GB)/
24.99 (unlimited I think?)
setup: FREE with 24.99 option - not mentioned with other option
modem: FREE with 24.99 option - not mentioned with other option
extras: 250mb webspace (as additional extra)
Virgin
monthly:
24.99
setup: FREE
modem: 9.99
extras: 10mb webspace - NO contract
Pipex
monthly:
19.99 (1GB then 1.95 per GB) /
23.44 (unlimited)
setup: FREE
modem: FREE
extras: 50mb webspace
I went with Pipex (unlimited option) and these are sort of in my order of preference. Plusnet seemed to be quite cheap - but their website didn't describe their products very well (they had 3 or 4 diff ones - the only one that mentioned setup costs was the 24.99). The Eclipse site was also bad at describing its products - the links didn't seem to bring up a very relevant page.
Weird how you choose a product based on their website navigation and content but there you go... I guess it makes sense with ISP's though.