UK / EU seat regulations?

[gilghana1]

Dear all,
looking for some advice regarding seat regulations in the UK, but also EU if anyone knows. Basically what I intend doing is fitting a 2nd row of two seats (forward facing) in my troopy. Now I know (well I think!) that inward facing side seats are illegal (my troopy is the 13 seater variety) and would have to be permanently removed before I put the troopy through an SVA - all this is assuming that sometime in the nearish future I may be registering it in the UK. Now I could get all the relevant part numbers and buy the Toyota 2nd row, but it would probably cost a small fortune. On the otherhand you can get a set of seats designed to make carrying people legal in a van. These look good to me, coming in folding varieties, lockable box varieties etc. I also have a few 3rd row LC 105 seats I could probly use. So, the knowledge I am looking for is:
- In the UK is it acceptable to DIY van seats (they would of course have seat belts and be mounted securely with spreader plates under the floor etc)
- Would such a seating arrangement be a bone of contention in an SVA, being obviously not part of the original vehicle.

In Africa things are a bit different, as a deck chair in a transit van would get like a 5 stars from the Ghana road safety body and putting 25 jerry rigged "chairs" in an Hiace (plus a bit of sitting space up top) is seen as totally normal.
TIA,
Gil