Now I am retired I recently converted my builders van to a camper van. In the rear it has two side bench seats that convert into the bed. My question is, as it has only seating for three in the front am I allowed to carry passengers in the back on the bench seats which havn't got seat belts fitted as there is no suitabe mounting points and they are not that effective used sideways on anyway.

My gut feeling is no. Rear seatbelts became compulsory years ago, but I guess it depends on the DVLA/VOSA or whatever regs.
How many seats on the V5? that is a starter.

According to this its legal but not advised.
https://www.campervanlife.com/vehicles/seat-belt-regulations/

Thanks Loggyboy, very useful.

Having been in a car crash in January where a seat belt probably saved my life I'd really not be happy with un-restrained passengers in the vehicle myself - (be it legal or not).

I'd consider not just the safety of the un-restrained passengers, but the potential impact upon other passengers. Bodies are pretty fragile and having them fly about inside a vehicle poses significant risks to the other passengers.

When you say camper, i presume you have already informed your insurer?

It's a must.