In the 80's it used to be that, in France and Spain at least, camping discreetly was tolerated almost anywhere outside the big cities. Even if you were caught unprepared somewhere in the middle of nowhere you could ask a farmer and they would gladly let you pitch a tent in a field. Nowadays it is a little more iffy. Last year in southern France there were cases of police harassment because illegal immigrants from North Africa were camping in small "tent cities". You need to exercise some caution but it is still doable. Just be aware if you haven't done it recently, especially in Summer. The locals are overwhelmed by people from North Africa and East Europe looking for cheap accommodations. Looking the part of the intrepid cyclist and appearing "clean" always helps. Also, if you speak a little French that goes a looong way towards being invited to pitch your tent on a field for a night. Of course, YMMV, especially if you are young and look innocent enough.