A few tips (in no particular order):
1. Consider buying a GPS receiver such as the Garmin 2610, available from
www.gpsw.co.uk. Not essential by any means, but can take the stress out of navigation and finding fuel/hotel etc.
2. If you don't buy a GPSR, get a copy of Microsoft Autoroute for your PC. You can use it to plot routes, calculate distances and estimate times - useful for trip planning. You can use Michelin maps for on-the-road navigation, but planning on the PC is much easier.
3. Do an internet search on towns on your selected route, or plan your route around interesting towns or features. You don't want to spend all day on the bike.
4. Accommodation is relatively cheap. You can ask at tourist offices, or use one of the cheap hotel chains like Formula 1, Campanile etc (check the Internet).
5. Be aware that petrol can be hard to find on Sundays, and most UK credit/debit cards don't work in the French supermarket automatic petrol pumps.
6. Go with the flow, don't be afraid to change your route. If you are running late, you can make up time on the autoroute.
Hope this helps. The main thing is to do it yourself rather than relying on routes suggested by others - you get a much bigger sense of achievement. Biking in France is easy and enjoyable.
Glynn