Yes, in France, the helicopter ratings are not yet JAR compliant for a few more months.
I do not know about converting from an ICAO ATP to a French one, but I do know about the CPL or IR.
If you have an ICAO CPL, you will need to pass the written exam (JAR like), to follow a 15 hours (10h + 5h Instrument) conversion module in an approved flight school, and pass the flight test.
The +:
- you do not need to follow ground school to take the written test
- when we'll move to JAR FCL 2 (probably next year), your licence will become JAR compliant.
The -:
- the French written test is difficult. Not because of the level of the test, but because of some silly questions where you have to understand what the civil aviation wants you to answer instead of what would be the theorical correct answer.
- I'm not sure that you can have all parts of the written or practical exams in English.
For the IR conversion, bad news, you will have to do almost all the practical training in addition to the written test and practical test. If you have a JAR IR(A), then you can follow a short training, but if you've already an ICAO IR(H) you don't know how to fly an helicopter in IMC !!!
You will also have to pass an English exam, again completly stupid as it is focused on airline and not helicopter. Beware, lot of english native speakers failed it...
Patrick