Just to clarify JimL's point (if I dare!) of course he will be correct about when France adopted JAR-OPS, but its JAR-FCL 2 that has been the problem for French pilots. The French have very recently adopted JAR-FCL 2. So EC145pilot if you have / will be getting a JAR-FCL2 compliant licence there is no problem (don't know what a JAR-FCL3 licence is - a mistake I hope!). French pilots only having a French National licence have a bit of a problem as the UK CAA doesn't recognise the licence directly, though they can be persuaded to give a validation.
Regarding the salary, I think you can expect more as a captain but bear in mind you will not walk into a command if you have no offshore experience and no ATPL.
But I would expect that Parisians endure a higher cost of living that Aberdonians, though the coffee is better in Paris!..
HC