Bit of a bump but a valuable thread
About to need some prepaid data in the UK myself, was able to check the T-Mobile coverage map (O2's coverage map won't launch) and their deals seem pretty good, £10 for one month of free internet (unlimited email/web) and 500Mb for downloads/video apparently. They don't say anything about tethering though...
Question is, can I just pop into a T-Mobile shop and get a microSIM and be on my way?