Yup T3 (T25) is the future. Picked my panel van up for £900 with 12months ticket and 6 months tax. Spent about £2K including the van to get it is how it is now. Mines water cooled unlike Tobz's but is still a flat 4 boxer engine so makes all the right (and worrying) noises. THese also came with oil burners installed but by all accounts the factory dervs are pig slow, if you're lucky you may be able to find one someone has converted to a later TDI engine. I seem to recall a scoob engined one for sale recently for not much money.
For a purpose built one (Devon, Westy etc) expect to pay a fair bit more as they fetch a premium, specially if RHD as most are LHD imports. LHD isn't too bad in these as you rarley overtake anything in them! Check out eastfalia on google as he imports decent vans from germany and does them up if you want. Otherwise have a browse on
www.brick-yard.co.uk/forum or
www.club80-90.co.uk as these two forums specialise in the T3 and there are always a few for sale.
Finally you could lok at a T4, not that exciting but starting to get a following on the scene and more tuning/bolt on bits are becoming available. On the upside they're more refined and economical. A factory fitted camper will cost you an arm and a leg but a used panel or minibus shouldn't be much more than a T3 of the same spec unless it's the high output TDI.
Theres something to get you going bud.
Nick