Hello Michael,
I am writing to you from Poland, but I am a really fan of spending holiday in France. I go there every year with my family and we always want to come back there. We have been on Lake of Ste Croix twice and we always have had a big problem with finding a place , so my advice is to book a place some moths before. This is really fantastic place, especially that you can swimming there, walking, cycling, clibing rafting and so on. And thats incredible smell of lavende. This year we stayed on a camp near Moustiers St Marie http://www.provenceweb.fr/e/alaupro/moustier/moustier.htm- it is a fantastic city. It name is Le Moulin - it isn't very comfortable, but there is a very familiar atmosphere and it is cheap. There is also not so far to the beach - about 10 minutes. You must be carefull - many campings has a long way to the beach because they are on the top of hill. I especially recommend you the trip round the canyon - there are wonderfull wievs.
Have a good holidays
Kate