Seatbelt regulations for motorhomes

Apullara

Hi, I've just bought my first motorhome. It's a 4-berth Bessacarr. It has a fixed rear double bed and two facing long seats behind the driver and passenger seats.  

I'm not sure what the legal situation is with passengers travelling in the MH.  Since the 2 long seats face each other I didn't think that seatbelts were necessary although I would like to have them installed anyway.  I've read on the net that it's not possible to have seat belts fitted to these seats and that it is now against the law for passengers to travel within the MH.

Any help on this would be appreciated.