You are looking to stay for six weeks at the height of the season and, even though it is a little remote, most self-catering places located in the vicinity would expect to be able to sell all six weeks at their highest tariff, which, even for the smallest places, may well be € 500 a week. Indeed, many places may well already be booked for some or all of those weeks.
The local tourism site, which célestina has provided a link to above, provides in its turn links to properties which might suit you. They are likely to give prices but probably won't say on-line which weeks might still be available, you will have to contact them for that. Don't forget that they will require sizeable (and probably largely non-refundable) deposits for the booking, and then again when you arrive as a security against potential damage.
And again, as Celestina has said, you will need your own transport throughout your stay unless your relative is going to act as your taxi driver.
Oh, and I suspect that you are being a trifle optimistic in hoping to practice your French. Obviously local traders will speak French, but you may well find that most of your other contacts will be with tourists from outside France whose French is little or no better than yours.
Edited: 3 years ago 
