At last we are coming to France

After talking about it for 10 years we have at last managed to arrange our life so that we can do the move to France. However, we have selection of places that we think we would like to live in so we are taking a year driving around France with our caravan staying in a various places to see which suits best. As we are starting in the next couple of months, it will be colder and as my wife suffers from bronchitus we are going to drive down to Spain for a couple of months and then return to France in March or April. Can anyone recommend any camp sites on the route down from Dieppe to the Spanish border that are open all year round?