Hi Wigwam,
Friend recently purchased a high spec Audi A6 off cargiant in London - no problems - Flew into Heathrow Taxi to cargiant and got ferry back - only thing he mentioned was that You have to be prepared to go at short notice as they will only hold the car for 48 hours max.
A related question - I am going to go to UK to purchase 2005 Rav 4 Diesel in January - any advice on where I can get a list of dealers and also how often Revenue update then VRT calculator to take into account vehicles being 1 year older - Thanks