Where is Faillance in Provence? Do you perhaps mean Fayence in the Var?
I don't have any agency recommendations, maybe someone else does, but we have used the owners direct website to book (amazing) places a couple of times, often owned by Brits.
Otherwise i would recommend contacting the tourism office of the village or town that you wish to stay near and asking them for the rentals ('location') they list.
In the case of Fayence it is via
http://www.paysdefayence.com
Otherwise, you can try the Official Gîtes of France website, there are sometimes some lovely little places on there, particularly for a small family. We booked through this once and it worked well - again it is direct with the owner. Do note that with some Gîtes you have to supply your own bed linen and towels.
If you are looking for August this year you may find that the nice places, particularly in the popular areas of Provence, maybe quite booked up already.
Enjoy!
