Tracey, There are several good sites around Biscarosse and many more between there and Biaritz.There are of course many ways to get to France, I use Poole to Cherbourg to support my local port. I am lazy and must also take my holidays during school breaks, so if there is a site in C&CC Carefreee, or CC equivalent I usually book the ferry and the main site with them, and find my own sites for the rest of the time. It is of course a personal thing and I have booked direct with site and the ferry. I don't know what you want but if you have youngsters then then La Rive is as good as any that are on the lake. If you want the whole beach experience then Airotel Saint Martin at Moliets Plage is the place to be. I would avoid La Reserve as I found it to remote, and a bit captive, whereas I like a stroll in the evenings to local bars etc.
If you want any info on night halts at municipal sites let me know.
If you fancy a 2 day break at Poitiers a visit to Futuro Scope is to be recommended especially if you can stay for the midnight laser / hologram show ( not sure if its only on Fridays and Saturday nights). Parc de St Cyr is a good site if you do.
Anything specific you want to know just ask. Ray