Another option is to get a basic van and convert it yourself. You need to fulfill certain criteria to re-register the van as a camper with DVLA & to get camper van insurance (cheaper than van insurance). Off top of head I think you need a bed, at least one cupboard, a fixed hob/grill thing, a running water setup, and a table that bolts into place. Can all be done very basic. Shield insure self-builds, and will cover you while you get it up to spec (they give 90 days - after which you need to supply photos etc to prove you comply with the requirements).

Self-build website is http://www.sbmcc.co.uk/ and is full of good advice. Has a friendly forum for all the questions you might have.

Basically - its a way to get a very cheap camper van, and you can look around for a base van that suits your requirements & is mechanically sound.