Elizabeth,
Apologies for the above entries, something went haywire!
I took a caravan to France 4 years ago and keep it on site permanently in Beaune, Burgundy.
There aren't any real problems, we pay a small fee to leave it on site and pay the going rate when we visit.
We can take it off site to tour but we elect to pay the retainer to ensure that we keep the same pitch.
Insurance with UK companies is more of a problem, perhaps it may be better to buy a van in France if you are going to leave it there permanently.