there is some cheap stuff on ebay, guy i work with just bought some for his zwitter. cuts down noise, keeps the heat in.
its what the sound off boys use
have a look at this
http://cgi.ebay.co.uk/30-Sq-Ft-eDead-Origi-Sound-Deadening-Free-Fatmat-Cutter_W0QQitemZ330107318716QQihZ014QQcategoryZ1498QQrdZ1QQcmdZViewItem
I used some insulation on a roll from B&Q. Its about 2mm thick with a silver side. 1 roll covered the rear hatch, side panels, rear arches and front panel, three times! I stuck this on with some spray glue
On the floor i found some nice thick laminate floor underlay. Cost me £28! but it seems like good stuff. Cuts very well. Ontop of this i plan to lay my plywood sheet & carpet.
Still want to waxoyl & insulate my cab doors, but have to wait till my new exhaust & alternator arrive as the van is stuck in the garage and i cant open the doors!
Take a look at this site I've also been looking into cutting out all the road noise and having a snug van on an evening. Seems preety sound but note his mistakes and get it right first time.