The gift thing is not 100% guaranteed. A freind of mine who lives in Chicago sent me a new CPU for my PC. I got hit with ?90 tax charge which made it the same price as here.
As for the PCIII working I would be wary, I spoke to a PC guy at the NEC and he said lots of people have imported them (mostly from Germany) but they are not supported by PC in the UK, if you have any issues with it you're screwed.