Which caravan to buy was clearly going to be a big decision, so after a little research we bought the first one we saw!
(we didn't buy it on the spot, we left it two weeks and went to look at lots more, but fate seemed to be guiding us and the Lunar Quasar 546 we saw had 3 fixed bunks and a dining area at one end, a decent bathroom and kitchen, and a big lounge. It was as if someone had designed a caravan just for us!
Apparently you should buy a caravan with 2 more beds than you need, so we looked at a selection of 5-6 berth vans. The design and layout of the Lunar Quasar 546 were great. At 7.4m it's a big caravan, but we did the sums and our Audi estate should be able to pull it comfortably. (edit - that was before we loaded it with 20 crates of stuff!)
The guys at South East Caravans in Whitstable were friendly and more than happy to answer all our random questions and let us view a whole range of caravans before we made our decision.