Btw this is not a nfu one off , my son hAs done one the same with a different insurer.In my case as you know ours is a self converted ambulance insured with nfu, they insured it from the start, never asked what was going in it or anything else as far as I can remember, I just told them when it was finished, and the insurance just carried on as motorhome instead of van and that's how it has been for 8 years.
They have no idea what batteries I put in it. Or anything else for that matter.