Hi,
Assuming that you will be a UK state pensioner with access to the french health system at the UK's expense via S1, I thoroughly recommend waiting till you are established here before having the op.
I had mine done 2 months ago in the Libourne clinic and it was very satisfactory. Although some of the extras (private room television, telephone and surgeons extra fee) were covered in my case by a "top-up" insurance, they would only have come to about 650€ if I had had to pay them myself. The total cost , the great part of which was met by the state system was just under 10000€.