Information correct as of last summer:
France no problem mode C only.
The
official word from France is this:
It is also recalled that, in accordance to article 3.2.2.2 of the annex from modified June 21 (2001) arrêté, all IFR aircraft have to be
fitted with a mode S ELS transponder since March 31, 2007.
For VFR flights, mode S transponders will be mandatory in 2011 only for new Certificate of Airworthiness. Planning is that they
become mandatory for entering published area by 2014 (arrêté project on going).