Be careful.
I heard through some pilots here that the French CAA seems to severely fine and / or ground pilots without an ICAO Level 4 in FRENCH if they are caught on a "French only" airfield in France recently!
Knowing French is not enough, as well as it is not enough to know English. You need the paper to go with it.
Since I heard that, I won't even use a French greeting anymore on ATC as it is theoretically a violation.
So in France, unless you got a Level 4 exam in French you can show, keep away from "French only" Airfields.