I can elaborate m4tcc!
I bought a 2005 C4S which turned out to be a 2003 car, imported from Cyprus. The long and short of it is that it was mis-sold to me. Amongst other things it hadn't been HPI'd by the dealer, had more previous owners than advertised, more miles on the clock, an incomplete service history and no warranty.
I shall put a message out shortly too about imported cars. Mine came from Cyprus although the dealer never told me of this. It turns out that it is not insured for theft as a result. All UK spec cars, not just Porsches, come with a Thatcham Cat1 alarm/immobiliser system for about the last 10 years. As mine doesn't have one, despite having a Tracker Monitor fitted, my insurers, Norwich Union, won't pay out if it's stolen. My broker said that some insurers also do not cover such cars at all.
So to anyone who has anything other than a UK c16 spec car, check your insurance!!!