Just to make things confusing in the best French tradition, the 80kph speed limit on single lane roads is now under review and departments (really equivalent to Counties in the UK) can decide whether to keep it or go back to the 90kph limit. Some have already reverted and have changed their signs to show 90kph. If you're not sure (I'm not most the time and I live here!) stick to 80kph.
In the last year or so UK visitors getting flashed by speed cameras in France are now receiving fines through the post once back in the UK. You really shouldn't get flashed as there is always a large sign telling you that there is a camera ahead and then a sign with the speed limit on it.
The police enforce the drink/driving regulations more here as well. They can just put a road block up then stop and breathalyse everyone. They don't have to have any other reason to stop you. You're most likely to encounter one during the afternoon (after their 2 hour lunch!) or late in the evening. Although you are required to carry a DIY breathalyser, there's no penalty for not doing so. So save your money and don't buy one.
Regulations were introduced about having reflective stickers on helmets but this has been universally ignored as has been the requirement to wear gloves that have approval certification on them, possibly just a CE mark.
The "priorite a droite" (drivers having priority coming onto your road from your right) is alive and well still. So if riding on minor and back roads and through villages, keep an eye for junctions on your right. Even if you're on what is effectively the main road and there is a minor road on the right ahead of you, if this road has no white line or stop sign they have right of way and can pull out in front of you expecting you to give way to them. There are also roundabouts where the same applies. If there is no roundabout sign or white lines on the road, traffic entering the roundabout has priority over traffic already going round I.e. you can enter the roundabout without slowing down and traffic on your left has to give way to you! Get your head around that one! There are two of these within a 5km radius of me. Even the French can't cope with them.
Otherwise that's about it. Have a great and safe time.