Knocked my libre off on a door post whilst in France for a few days. Went in to a chemist and asked if they sold sensors, yes was the answer. Pleasantly surprised I was only charged €35 euros...not sure if the same all over France, but they seem readily available and cheap!
Yes!
As far as I know they're usually 37 euros in France.
I had a friend and an uncle visiting France for holidays and they've both visited multiple pharmacies to buy me sensors. So I now have enough sensors to last me until july next year, for 37 euros each instead of the 60 I pay in the Netherlands!
In the app it chooses based on your country, which is pretty stupid when you ask me. But having the Dutch app the French sensors act exactly the same as the Dutch ones, only the package is (very slightly) different. I don't even know what they use in France.
In France we us Mgdl so not the same as in the UK, or it was not when I lived in the UK 26 years ago, Sorry to say but I do not know if libre work on both depending on which meter is being used.