Converting my van to a camper...

I'm planning on converting my van to a little camper to do festivals with, and have a couple of questions about it.

It's going to have a raised floor all across the back, to allow for under floor storage, the walls will be lined with thin plywood and insulation packed behind them. Up in the roof I'm going to have a net hammock for storing soft things like my clothes, and I'm contemplating having a skylight, to let some more light in, since it's a panel van, rather than a minibus.

My question is this, I often give people lifts, but it's a bit limiting only having one passenger seat, and I don't want to fit another permanent seat, since I won't have the room for my bed. Is it possible to build a fold down seat of some kind into my conversion, out of wood, and have it legal? Am I required to fit it with a seatbelt (I assume so) and are there any structural requirements for a passenger seat?

Cheers,

LBV.

My mates fitted a rock and roll bed in his T25 and fitted seatbelts, he had to have it reMOT'd but that was it.

http://www.ukmotorhomes.net/motorhome-faqs.shtml#seatbelts