D,
I'm going to recommend the following to you:
1. Eriba Puck or other touring caravans from Eriba.
Cult vans designed in the 1950s by a German aircraft engineer, these have the same build as an aircraft (welded tubular steel frame), still in production, still look roughly the same as when first introduced, these are quality products that hardly depreciate. And most are still around...
Disadvantages: Expensive to build, expensive to buy. And since there's a cult following, you'll be competing for each van as it appears...
2. KIP Kompakt
These Dutch pop-top caravans are highly regarded, light to tow and a quality product.
Disadvantages: May be difficult to locate in the UK
3. T@B
German designed caravan that looks like an egg, small and pert.
Disadvantages: May be difficult to locate in the UK
All of the above will have the non-caravanner smiling, good quality means water leaks shouldn't be a problem, or you could just buy another white box...
Robert