Second hand caravan: Things to look out for

In a few weeks I'll be looking around for a second hand caravan for me and the missus. This is home for the next six months.

What do I need to look out for in Britain? Mechanically, I can do the checks: wheel bearings, underneath not rusted through, tyres have enough tread left.

What other bureaucratic things do I need to take in mind? MoT? Tax? Finance still left on van by previous owner? Is the bloke selling the legal owner?

Thanks.