We get a great deal of enjoyment from our own local section of the Rigole d'Hilvern (V8) which runs from Lorient on the south coast to St Brieuc on the north side. Given that we still spend short stints in Brittany that route will do just fine for a few kilometres each day or so. But, when we have the planned camper van and a bike rack and maybe even stay in France for longer than just two weeks at a stretch... Well, look out Jules Verne (he was born in Nantes)... It'll be 'Around the Bretagne Peninsula in 80 days'!
Give us a wave! And Bon Voyage if you get out there too... (btw I got the book detailed below, out of the library recently... well worth buying if you move to Brittany and love to cycle).