Anything to look out for on an imported but UK spec TDi Quattro?

As far as I know, no, nothing, not if its a personal import and full UK spec. My old 2002 S3 was bought in germany (new and unregistered) and then first registered in the UK - it didnt even show up on the DVLA as being imported because strictly speaking it wasnt. The only thing you have to check is the engine code, as it probably wont be recorded on the V5. Other stuff like weight might not be either. Not sure if this is a problem, but it never concerned me. Warranty on non-uk bought cars was 2 years instead of 3, but thats well out now anyway as you say.

check insurance though, most wont care as long as its a full UK spec, they only care about 'greys'.