I stumbled across this today and thought it was worth sharing, I’ve got no link to the company.
Campal have a Kia PV5 Passenger kit that looks like a fully removable boot module, aimed at turning a 5-seater into a weekend micro-camper without drilling or permanent changes. Their page says it includes a fold-out bed platform, 8 cm cushions, a heavy-duty slide-out kitchen drawer, and a central rotating table. It also claims you keep the 5 seats usable for weekdays, and the whole thing sets up in about five minutes. 
Headline details I noticed:
- Custom fit for the PV5 Passenger
- Standard bed length 180 cm, with an option to extend to 200 cm for a surcharge. 
- Listed price: £2450 (inc VAT). 
- Main unit weight: they say about 70 kg
Key drawbacks:
- No fridge or space for one
- No water tanks
- Seems like the space under the seats is hard to access
- Under-floor space feels under-utilised
Link: https://campal.co.uk/campal-kia-pv5/
