He is a baby western whip snake. He is about 30cms long. They can grow to around 2 metres long. For information about beasties in France and elsewhere, go to John's Suite 101 site.
http://reptilesamphibians.suite101.com/article.cfm/harmless_french_snakes
http://reptilesamphibians.suite101.com/article.cfm/venomous_french_snakes
http://reptilesamphibians.suite101.com/article.cfm/newts_and_salamanders_of_southern_france
http://lizards.suite101.com/article.cfm/lizards_in_france
The snake was released into the garden and disappeared in only a moment. His body is a dull brown colour, so he blends well into the foliage. His head has beautiful markings.
Let's hope by the time he is any bigger, he has moved on.