I don't need to clear customs on leaving France?
As far I as am aware, yes you do.
Couple of years ago, we were not allowed to depart from Caen, for the UK, until the Customs came back from their leisurely two hour lunch!
Mind you, we went to Le Touquet a few weeks back, on a Saturday. The Customs office was empty when we arrived, and still empty when we left (neither time was lunch hour). So did we break any French laws?