Don't forget your driving licence and you wifes also.
You should by law have a spare pair of glasses in the car if you need them.

Do not speed through little villages and small towns. When you see the sign for the name of the town, you are entering a 31 MPH (50 KMPH) speed limit. When you see a similar sign with a diagonal line through it that is the end of the 31Mph limit. BUT in both cases this may be changed into another limit which is like a UK speed limit sign, IE a circular sign with a number in it. Most Brits simply do not react to the town names as it does not register a a speed limit sign. The French can get very unpleasant if you speed by schools especially when there is likely to be traffic to and fro, often shown with a flashing amber triangle sign.

You can park in laybys and rest areas whenever and for as long as you like. France is very much a live and let live society. There is no antagonism between bikers and cagers or anyone else, unlike the UK. It is customary to pull over to let bikes pass or filter. The rider will normally say thank you by sticking his right leg out in front of his bike.

Petrol called essence is usually available 24/7 by using a chip and pin card. Most now accept UK cards. As in UK, supermarkets are usually the cheapest.

If you see lots of trucks parked around a non descript building around 12 noon, this will be a routier. I recommend you go there and eat. It will be a set FRENCH menu with about three choices for 10-12 euros. Usually 4 or 5 courses. including wine and often coffee. This will be real traditional French food and excellent value and bit of an experience.

Most supermarkets have a ready cooked food counter where you can get meals for as many as you like, 1 onwards. The freshly prepared food is usually weighed and put in sealed containers. very easy to put together an evening meal or picnic. France is very camping friendly.

As previously advised, get a free EHIC (European Health Insurance Card) card for each member of your party to obtain "free" medical care whilst outside the UK. search for it on the net, you can get them usually with just a phone call but check on the net. Anything you do have to pay for, keep the receipt and you will usually be able to be reimbursed when you get back to the UK.

Hope this helps. You ought to have a really enjoyable trip and not need a 1/4 of this stuff.