In reply to NZClimber:
Van insurance can be expensive because they tend to be driven by nutters who have more than an average number of crashes. There are quite a lot of cars that are essentially vans with rear seats but could well be cheaper to insure eg. small van size, Citroen Berlingo/Peugeot Partner, medium van size, Ford Galaxy/Seat Alhambra/VW Sharan.
Insurance can also depend a lot on your address, if you're not actually living here in your own house do you know anyone who lives in a nice safe area who's address you could use as your nominal UK base (for insurance purposes)?
Alternatively at £900 to buy + £3000 to insure couldn't you just hire a van if you're not here for too long?
Post edited at 22:18