Health
Remember your medications and have sufficient for you trip and bring your prescription just in case. It is not always possible to get them replenished in France. It may need a doctor's visit with the original prescription to get a new prescription valid at a French pharmacy. You are cycling where generally there is a lot more more sun and higher temperatures.
Sun Protection
Always use sun block on any exposed skin and if the ride is more than 3 hours you should carry it with you to re-apply. Do not forget lip block. Carry it with you and replace it regularly after drinking or eating. Sunburnt lips are not pleasant.
Hydration
You will need to drink more especially with the heat and the climbs. Consider whether your usual size of water bottle is sufficient. 500ml should be considered a minimum. Generally on almost all routes there are places to refill your water but not always so do not get caught out with no hydration. If you add Isotonics you will need to carry that to replenish it. I find a resealable plastic bag useful for powders. Dehydration is one of the biggest causes of cramp.
Energy
Climbing hills uses energy. Carry enough energy products bars, gels etc. so that your blood sugars levels will be kept up. Remember you may need more than normal. Bonking is not a pleasant thing.
Urination
You will not get arrested in France for urinating in public. However do try to be discreet and choose quiet out of direct sight places.
Comfort Break
Bowel movements
The rule here is do it before or after the ride. If you do get caught short during a ride the best thing is to stop at a village cafe for a coffee or tea and use their facilities. In extremes you can find a quiet and secluded place and use those paper handkerchiefs you brought with you.