Route to Calais

Picturesque, hilly, slow and twisty once you are past Ales heading north - but perfectly passable with a caravan if you are prepared to take your time as it can be quite a busy road 
A pleasant stopover for a few days part way up the route is Camping Chantemerle at Bedoues on the river Tarn a little way north of Florac. 

Its certainly possible, but slow, with good scenery. Before A75 it was my usual route.The The N88 is good once you are up the hill and onto the plateau of the Massif Central. An alternative and perhaps less twisty route would be to go up to Aubenas on the D904 and take the N102 to join the N88.