The AA and OS maps recommended above will be of limited use then!
I have toured across France 'ad hoc' using just a* GPS (an older Etrex model) and some kind of reference map** for planning, and it's completely do-able and trouble-free. However I do have 'proper' maps (ie Garmin's own, possibly expensive, maps) rather than relying on OSM, and I suspect that makes a difference.
* Actually 2 GPSs, because there are two of us cycling together - with our 2 units set up slightly differently, this gives a huge confidence boost when they agree at each decisioin point - and if they disagree, it means we can choose the better-looking option on the ground.
** In France, I have used a tablet in the past but now I would take a large-screen smartphone, with Memory Map installed, and IGN mapping which is a bargain with MM. I would use this as a planning aid in the evenings. IGN maps on a 5" phone screen are just fine. I would also put OSM maps on the phone, because that is pretty good now in most of France, except only a few un-touristy bits of the interior, and it is very good for identifying usable off-road options such as bridle paths atc. OSM is also the best map to have in more exotic countries, such as India.
Our modus operandi then is simply to have a general idea of each daily destination, then bar-crawl our way there stopping at 20km intervals. With a drink in one hand, it is a simple one-handed job to scroll the GPS map on to the next 20km-ish stop, click on it and choose the option 'Go To'.
Since we use hotels, not camping, the GPS is also very useful when we get near, for locating nearby hotels and maybe even providing a phone number to ring ahead.
I'm not saying we do this always - actually we are compulsive over-planners and usually have all our stops scheduled to the nearest hour, before we set off - but we have done it, and it's fine.
The alternative to the bar-crawl approach is to program the complete daily route each evening - to do this simply start a 'new route' (don't forget to name it) and then use the map to click-click to your destination, clicking on each road*** you want to use along the way. Don't bother with towns, just click once on your way in and again on the road you want to be on when you leave town. Make sure you're clicking on a road and not on some spurious feature such as a contour line! You have a max of 50 clicks per route - should be more than enough, in central France probably 10 would be enough, for a day.
*** don't click on junctions, click part-way along each road you want to use. Like this:
See this how-to:
http://www.aukadia.net/gps/lwg_41.htm