JustKampers for me. I had two vans with them. New van is on agreed value, which I can increase once the conversion is complete. I changed the reg on the old van easily via the app so I could keep the plate.
I sold the old van this week, and they helpfully held the insurance on a dummy plate to the end of next month, so I will be able to transfer a full extra year’s no claims to the new van. No, I’d never heard of that either.
So far they have been good - lowest price for my camper, OK to insure a conversion in progress, and handy app to hold the documents and do some updates.