Municipal sites France, how to book them??

mmd333

We are looking for a stopover site within approx 2hrs of Calais, heading towards Reims.  We dont want to pay alot but want nice clean toilets/showers.  We have found some municipal sites on ukcampsitereview website but when we click on them it directs us
to what looks like the local town's website.  Can you book a municipal or do you just turn up and hope for the best.  Alternatively, can anyone recommend a nice clean site approx 1-2hrs from Calais in the direction of Reims.