There is a CMAS to PADI equavalent, you do not need CMAS qualifications simply qualifications
recognised by CMAS, which includes PADI.
PADI OW is equivalent to CMAS 1 star
PADI AOW and higher is CMAS 2 star
To dive deeper than 40m you need CMAS 3 star - there is no PADI grade at all that meets this requirement since PADI is a no-deco agency.
CMAS 2 star allows you to dive to 20m or to 40m with an instructor accompanying you.
Where are you going? The area around Marseille is very good for diving to 40m If you like wrecks the Planier Island just off Marseille has some very good ones no deeper than 30m.
http://scubaspot.free.fr/epaves/chaouen.html
Chris