The actual term is motor caravan apparently! Since 2012 the rules have changed but always double check with the DVLA.
This is worth looking over before you start (unlike me!) as it may affect your layout. In my case the bed we fitted first was not the regulation 180cm. My bed was across the width of the van and slightly shorter than the 180cm so we had to redesign the interior and rotate the bed 90 degrees so that we could get the full 180cm.
Infact they have a load of useful stuff here…
https://www.gov.uk/government/collections/vehicle-safety-standards-information-sheets
…including regs for driving urban buses on motorways and extending your vehicle behind the rear axle, neither of which I’m doing but you might.
I think the regulations (at the time of writing) boil down to:
Minimum Features In order for a converted vehicle to qualify as a motor caravan it must have certain minimum features, as follows:
1. a door that provides access to the living accommodation;
2. a bed, which has a minimum length of 1800mm or 6 feet. This can be converted from seats
used for other purposes during the day but must be permanently fixed within the body of
the vehicle;
3. a water storage tank or container on, or in, the vehicle;
4. a seating and dining area, permanently attached to the vehicle. The table may be detachable but must have some permanent means of attachment to the vehicle. It is not good enough to have a loose table;
5. a permanently fixed means of storage, a cupboard, locker or wardrobe;
6. a permanently fixed cooking facility within the vehicle, powered by gas or electricity; and
7. at least one window on the side of the accommodation.If the vehicle has all of these features present, permanently fixed and installed properly, then it is a legal requirement to have it reclassified as a motor caravan on the V5C.
Seems pretty straightforward aside from the use of the word ‘properly’. Can you get it converted on a V5 if it is not ‘properly’ installed… what is ‘proper’? As a conversion can I just install myself? I assume if you intend renting it out then the gas and/or electrics must be signed off by someone qualified but if you are not intending renting it out…?
See these links for some more details:
http://www.diy-motorhome.co.uk/Article/keeping-diy-campervans-legal
https://www.gov.uk/change-vehicle-details-registration-certificate/what-evidence-to-give
http://www.caravanwise.co.uk/motor/diycamper.html
https://www.gov.uk/change-vehicle-details-registration-certificate/changes-youll-need-to-update