I had a similar prob when I picked mine up, bought it on Easter Saturday 2003, was told it would be ready to collect in 4 weeks, 4 weeks came so I called them, they told me they would get back to me, no return call so I phoned again a few days later, again no reply. I phone again (5 weeks now) and still didnt get much sense out of them (I did actually get to speak to someone who knew something this time), couldnt get a numberplate out of them to sort out insurance either.
After a further period of nothingness I called them again, spoke to the salesman who dealt with me and would you believe it the car is sat there waiting for me! Got the plate, sorted out insurance that day and picked the car up two days later.
I spoke to quite a few people on various forums etc during that period and a suprising amount mentioned that it probably got damaged on its way over or something. Thankfully the car was in perfect condition (and has never rattled!) A small sticker left under the seat had a build date on it, this was about a two weeks after I bought it so it took one hell of a long time getting to the UK.