Sorry to be so late in replying - probably too late, but others may find this helpful.
For twelve years now I've use Camping Le Port at La Suze-sur-Sarthe. It's about ten miles downstream from Le Mans on the banks of the R. Sarthe. The site's municipally run and won't win any prizes, but it's cheap and clean even if in need of a lick of paint.
Resident managers Dominique and Richard have limited english, but are very helpful.
The site is busy mid June when the Le Mans 24 hour race is on, but otherwise quiet. All facilities are available within walking distance: Super-U supermarket, d-i-y store, chemist, bar, restaurants and hotel, hole-in-the-wall, boulangerie, swimming pool.
The site has hot showers, loos, washing machine and washing-up facilities. Every pitch has electrical hook-up.
Mandatory eye tests for drivers over 70 being proposed by HMG. Good or bad?
