Hi Daniel
I spent 10 days last year at a place called St Jean De Mere which is about 30 minutes (driving) north of La Rochelle, the harbour there was a drying harbour with a 6 hour or so tide window in and out, all the moorings were swinging so a tender would be necassary, the harbour fee's for visitors were so small it worked out about £35 for a week
The slip way there looked good and easy to launch and recover, the harbour office was on one corner and psoted tides and weather daily for the area on a notice board.
Only downside i could see was they didn't actually have a compound to store a trailer in so you'd have to take it to where ever you were staying and ask nicely
and you'd need to have a small tender to get on and off the boat.