I have to agree with Richard about dealing with cars in France. I used to be in the haulage game, back in the late 60's and up to the 80's, and it was always a slow job getting trucks repaired. We had Volvo's and Scania's and the crazy thing was, if we broke down and were towed to a local dealer, they had to contact either of the manufacturers in Sweden, to get authorisation from Ireland, and to order te parts from Ireland, before they would do anything. So you could be stuck in France for a couple of weeks before you got going again. Unless you did the job yourself, which is usually what happened.
A guy I know had a gearbox break, in Italy, and, after a good few phone calls, managed to find a second hand box some distance away. He mabaged to buy it and get it transported to the restaurant/bar, where he was parked, and with help from another three or four drivers, changed the gearbox and left the old gearbox sitting in the bushes behind the restaurant !! You have to understand that, in those days, Italian truck stop restaurants usually had very large carparks, maybe an acre or so, so nobody was bothered about an old gearbox just left in the bushes ! Somebody would probably come by one day, in an old Fiat truck, and rob it anyway.
I think, correct me if I am wrong, that in France you can't modify the engine, gearbox or running gear of a car, without some sort of permission from the manufacturer. You can fit body kits and different size wheel rims, and you may be able to change shock absorbers and springs but that is about it. I believe that it has something to do with the original build and design criteria, and if you change major mechanical parts you are contravening the factory specs. The same thing has happened in Ireland because the government brought in a Spanish crowd to do the annual road tests, and they test cars using the manufacturers specs, so you can't fit, for instance a straight through exhaust on your car as it wasn't fitted as standard. And they will fail you.
I have heard from young guys that I sometimes meet, with cars like Renault 5 Turbo's, or Escort Turbo's, Escort RS 2000's etc., that they are being failed for fitting things like dump valves and for chipping the engines, and also for lowering the car too much.
Lastly, there is a saying in France that the French don't like foreigners, but Parisians don't like anybody at all, including the French themselves. I spoke pretty good French, back in the days, and I have to say that it was always my favourite country to go to. I spent a lot of time there and got to know it well. I spent two years working for a guy up in Brittany and I loved every day of it.