The best camping deal we have so far has been in Noyers-sur-Serine but it is a little obscure since there is no regular reception.
The facility is equipped with electricity, hot water and toilets, but no soap or toilet paper. No wifi but you might get Internet at the library (bibliothèque).
To get the key to the gate you must go to L’Epicerie Vival, open from 08:00h-19:30h or Hôtel Ville opened until 18:00h. A €15 deposit is required for the key (clé).