Do you want to hire privately from the site, or would a Eurocamp, Canvas Holidays, Keycamp, or other tour operator mobile home be OK? If the latter then have a look at their websites. All the sites used also have touring pitches.
The 'Les Castels' chain of sites all hire their own mobiles - again have a look at the website for information - again they all having touring pitches.
I have heard good reports about the site Le Cormoran, which has direct beach access, and is in Normandy - but haven't been so can't give any more details.
Camping Du Letty in Brittany also gets good reviews and has direct beach access - but again I've not been.
Friends of mine liked the site Port L'Epine which was directly on the beach.