My first real taste of traffic-free routes in France was in Bordeaux. Alongside the broad river where the Cruise ships disgorge there’s a food market, cafes, antiques and a cycle track.
Getting there could involve taking your own bike on the EBE Bike Express or similar from the UK (by bus) or flying to Bordeaux airport and renting your ride from Bordeaux Scooters.
Le Deux Mers is one option taking you across France via the Garonne and the Canal du Midi to the walled medieval city of Carcassonne. This one is for improvers as essentially most of it is flat. Allow seven to ten days of biking to make the most of sights, smells and tastes along the way. (Double this for the return!)
Another option I have taken (four to five days) is a loop up to St Emilion. This was essentially a slower and more cultural trip as I had learned to slow down and absorb the surroundings.
The bicycle and panniers below were hired from Bordeaux Bikes and Scooters (essentially the same spec as my own equipment).