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we went to France in feb this year. (Disneyland) yes to triangle, fluorescent vests (at hand not in boot) light deflectors and worth having a spare bulb kit to. if your caught with any bulbs out its a fine. breathalysers used to be mandatory also and technically under french law still are, however the police are officially not enforcing the law so you will not be punished for not having one making the requirement to carry one redundant. (This was something I believe to do with the minister who brought in the requirement, having an unfair affiliation with the breathalyser manufacturer or something like that)
My Kadjar (with it being a french car and all) although a few months off being 3 yrs old still came with the original triangle and yellow jackets and mini first aid kit in the boot in a red holdall. have you checked if yours is there?
It is illegal to have speed camera location on your sat nav device and after much head scratching on how we were supposed to stop google maps pointing out where the speed cameras are we eventually realised (once we were in France) that google maps automatically restricts that function for you.
Of course you'll need a GB sticker unless you have a registration plate that has the blue European moniker to the side of the plate in which case it is not required....thats if we are still in the E.U. at the time of your trip!
If you're taking the ferry? we had a ferry booked for 7-30 am and arrived an hour early. Nothing to do but sit in your car and wait ...except we were told that they were pretty quiet and just put us straight on the ferry docked in front of us 'Bonus'
I remember it being quite confusing in the gas station to know which is diesel and which petrol (my french is really terrible) google translate was a lifesaver.
have a great trip I loved France.