I'm using CS3 downloaded from the Adobe US store. My cousin paid for it on his US credit card - saving me about £200. There's no problem using it in the UK. I checked with Adobe beforehand and they said it would be fine, but if I wanted support I'd have to contact Adobe US rather than Adobe UK. If I upgrade I might have to get that from the US as well - I'm not sure if a UK upgrade would work with a US serial number - but obviously that will be cheaper as well, even if I get a CD shipped over.