My pals are down there at the moment. They caught a late train, by my standards, at around 08:30 on Friday morning and got there Sunday, so 2 overnight stops. You could easy do it with one stop, it depends how much you like riding bikes. To get an idea of petrol cost, when I did a touch short of 2000 miles around Scotland earlier this year, it cost £248 in petrol, and generally it's more expensive in France. I'm going next week, estimating to do around 2,500 miles and don't expect much change out of 350 quid.