A telephone call to Camping and Caravanning Club . They are happy to welcome me to their sites as long as the conversion is properly and professionally done.
What they don't want are people driving up in any old van and wanting to sleep in the back.
I copied and pasted this next bit from the Camping and Motorhome Clubs' site:
The Camping and Motorhome Club welcomes caravanners, motorhomers, campers, campervanners, trailer-tenters, and anyone else, regardless of whether you own, hire, or borrow.