I too would recommend the municipal at Troyes. We have overnighted there a number of times, as it is ideally situated for the cross county/motorway divide on our journey - whether coming or going. It has always been busy in June, although we've managed to get a pitch. Walking distance to town - which is great, as we've usually been travelling for a couple of days by then. The one thing that always strikes us as odd (so we must usually visit on our way North!) is that the separate the ladies and gents showers etc.!I can thoroughly recommned the campsite at Geraudot mentioned by Dusty. Very pleasant,overlooking fields; good facilities, welcoming management. Swimming available from the beach on the lake and good cycling around the lake and another adjacent one. It is about 15-20 minutes to drive into Troyes from there. Incidentally, do not miss the centre of Troyes, which is a picturesque old town.
Bonnes Vacances.
Paul