You dont have to declare anything in too much detail as long as it describes the exterior okay. It could be a camper, an MPV, people carrier but the DVLA told be that the police would be happy with panel van/windows.
Are you concerned about converting a panel van into a camper? I converted a Window Van into a camper but as they ( and pre2009 Kombis, Shuttles and Caravelles) are all type approved as M1 cars then there's no change in speed limit to worry about so there's no reason to ask for the body type to be amended.
Strictly speaking a 2010 Kombi is type approved as a van (N1) whereas Window Vans, Shuttles and Caravelles are still M1 cars so Kombi would need changing over on log book to motorcaravan to get higher speed limit. In practice some people on here have been clocked for speeding in Kombis post conversion. This appears to be caused by whatever database the police cameras use not being updated, others claim that post registration conversions don't count but I've never seen legislation stating this so I'd hope any tickets could be overturned in court.
Only downside of using a car is that the VED is a bit higher.
Personally I went for a Window Van as it was cheaper than a Shuttle, its fully glazed from the factory and there aren't any seats, ducts or panels in the back which need to be removed prior to conversion.