@ Val A. Same as buying at home. In my case I had to act quickly as I was after a rare model that was nearly sold out. After tracking it down, and checking out the dealer concerned, I sent them a deposit by bank transfer to hold the vehicle until I could get time to go over for it. They sent me a contract for signing, which I did, adding the caveat that the caravan would have to pass inspection by me on collection. That was 2 months ago, So on arrival it was a case of checking all the paperwork, checking the operation of every window, switch, and function, hooking it on, fit my number plate and tow it home after a brief explanation as to how everything worked as a lot of the documentation was in German. Their second hand stock was in impeccable condition although most were of the 2.5m wide variety. "Caravan Park Thrun", I would highly recommend them, if you deal with the guy I did, Andreas Fries.
Again, what took me over there was the layout of the caravan, I did search all the UK manufacturers, buy none had any as standard to suit my particular requirements.