The seating in campervans and motorhomes is absolutely central to their design. Getting the right seat and bed combination will make or break your conversion, and choosing these items will almost certainly dictate the rest of your van's layout.
Staying the right side of the law in terms of vehicle regulations is obviously very important. The regulations state that all new vehicles have to have seat belts fitted on all seats except those seats intended solely for use when the vehicle is stationary. It is also now the case that if you do have seat belts in the rear, you are only supposed to take that number of passengers - i.e. you shouldn't be carrying more passengers than there are seat belts.
For a seat to meet the European NCAP pull testing, a 2 seater seat needs to withstand 6 tons of pull and a 3 person seat needs to withstand 10 tons. The PSV test also includes a seat belt and anchorage test as part of your MOT, and seats that do not meeting regulations or which are not properly tested not only pose a danger to your passengers but also to the driver if the seat does not keep the passengers restrained in the back of the vehicle in the event of an accident.