Where on earth did you find those Spongebob? Actually, for some unknown reason I quite like the car/van hybrid!
Being serious (briefly, I promise), this is like a new bus, with a warranty etc. Come resale time, the buyer is going to take a batttering: with some wear and tear an no warranty as a private sale this suddenly becomes a <£20k bus.
Just look what else you could have for 35 grand! http://www.autotrader.co.uk/classified/advert/201211457338684/sort/default/usedcars/model/db9/make/aston_martin/quicksearch/true/radius/1500/postcode/wr13bx/page/2?logcode=p Hmmm. DB9 or VW camper? DB9 or VW camper? It's a no brainer. I'll take the DB9 please. Probably returns the same mpg.
For £35k I'd want the "one off roof canvas" to fit a lot better than it appears to in the photo. £35k my arse!