We had a wedding here just over a year ago. We were able to use the local Catholic church (although we are not catholics ourselves, the priests view was that the church was for everyone). We did use an anglican minister Ben Eaton (beneaton@orange.fr). He came from Frejus to Bargemon. He was a very amusing and sincere minister. He does like to meet the couple in advance and did, in our case, have the couple make a promise in the church to one-another.
The marriage was conducted at the Marie before the church blessing. As your marriage is taking place in the UK first, you may still need a copy of the marriage certificate for the minister to see. It was important because one cannot go ahead without the other? Maybe thats just french law.
I hope this is of some assistance to you. If you need any further assistance with anything please don't hesitate to contact me. Good luck with everything.