I myself did the conversion thing from an Oz CPL/IR/ME (Navair Sydney) it's long and cost me around 30 000Au$ since I had to seat for all the french exams (ATPL) and to the conversion course of the time (1999) now it's slightly different , first you have to do a evaluation then training and tests.
To be honest if you don't speak french forget it although nowadays we speak Jar-Ops the french CAA (DGAC) still is reluctant to give pass unless you have significant hours on JAR/Far 25 aircraft done in an other Jar country (holland,GB,belgium,.......ect)
So maybe it would be better for you to see the conversion thing in GB
Ciao et bon courage