The 'priority right' thing is probably the trickiest thing. In some instances cars emerging from a minor road on your right, have priority to pull out in front of you as you travel down a normal major road with no obvious road markings.
Just give this a read and keep an eye out for yellow diamonds.
http://www.drive-france.com/faqs/get-your-priorities-right/There are also roundabouts with similar odd rules. Priority coming on, but not once you are on the roundabout. just look for road markings.
Have a check, but I have heard before that when there are big bike events on at Le Mans, they have a free biking lane on some of the tolls.
Never experienced it myself but was having a good chat with the other bikers at the ferry terminal.
You'll have a great time! French roads are ace and French drivers seem to be totally switched on looking out for bikers and will often drive along the verge to allow you to pass!
You'll often get a big wave from oncoming bikers (instead of the UK/left hand driving nod).
If you want to be to the letter of the law.. you might have to buy some reflectors for your helmet, adapt headlight angle, breathalysers, spare bulbs, GB/euro number plates or sticker and a high viz. But check online.