Nissan civillian bus/motorhome how many passengers

does anyone know what the rules are regarding the age of passengers not needing a seatbelt in a bus,`93 nissan civillian motorhome,its still registered as a heavy goods/bus,or even if you are allowed to take passengers in it
it has a drivers seatbelt and passengers seatbelt,the seating down the back doesent have belts.

With a motor home usually you would need to have seatbelts per berth, so if it sleeps 4 you will need 4 seatbelts for certification. If the seats are sideways and face the centre of the vehicle then only lap belts are required. For you to take advantage of the fact that the vehicle is registered as a passenger bus, the seats would have to be in the origonal position that they were in when the vehicle was first registered ,, or they would need certification,, Seats and seatbelts when changed or installed need certification for mounting and anchor points.How ever if you have seats and seatbelts installed that look professional, I think they would be accepted at time of COF and you would have no problem,, as to the question re an age limit wereyou dont have to wear a seatbelt, I dont quite understand that, I think that wearing a seatbelt would be more important than finding a way around it. Most vehicles state the number of seats in them at time of registration.