Seats aren't actually crash tested - they are put through a static seat belt anchorage pull test.
Camper vans are still a bit of a grey area but lots of new regs are being put in place at the moment which will make things trickier for small converters / diy / dodgy rock roll beds. If you want to be 100% safe in that van then the seat should be type approved to M1 standard (highest passenger car loads).
This alone does not make it safe - the installation also matters. If fitted to a brand new unregistered vehicle, then one sample should have been pull tested and type approved in a bodyshell (which scraps both the seat and the shell). I think camper vans currently escape this as a legal requirement (but not for much longer - and most major manufacturers test anyway to show due dilligence).
If it is fitted to an already registered vehicle, then it does not need testing but should be installed with the intention of being able to pass the test (e.g. it needs more than a few bolts and washers through the floorpan.....)
Reimo's seat is approved but also uses the body structure for the upper anchorage. The RIB seat looks good, and Scotseats do an M1 approved bed seat (the test cert on the website was signed by the guy sitting next to me...)
http://www.scotseats.co.uk/bedseats2.htm
We gave up on camper vans after having kids (wanting to strap something precious in the back). Now got a new tent and Dispatch Combi (factory fitted M1 seats but no bed) with a grille and extra bike lashing points to keep kids and bikes safely apart!
