Consider staying at a municipal campsite.  Most towns there have municipal campsites which are usually very reasonable priced, with acceptable facilities, and within walking distance of shops, restaurants and quite often sporting facilities.

Me

The discount card for early and late season, the 2007 book at £6.50, contained 1134 camp sites in 17 European countries, discounted to 10€, 12€ or 14€ / night.

See their web site for details

Me

Park Resorts have nineteen parks that take tourers and out of season you can stay for as little as £7.00 or £5.00 / night. 

See their web site for facilities and latest offers.

Me

Do not like Aires myself but a very good way to camp economically, especially if you only there for the night.

Campingcar-infos has the most comprehensive list of current Aries but it is in French.

To me a better idea than Aires are France Passion but there are fewer and you have to subscribe yearly (28€ for 2007).

Its very like the CL / CS system operated by the CC and C&CC in the UK but staying free at participating vineyards and farms.

See the website for more info