i know this has been aired many times, but worth a new heads up, as there has been a few threads about campsite costs lately but no mention of these very good free sites , if you are new to France travel, these are free secure sites much like britstops here , we used them quite a lot when we started going to France, and always found them excellent, and can throughly reccomend them.
https://www.france-passion.com/en/
https://www.france-passion.com/en/