There is also a problem with non English controllers issuing instructions in English without clearly articulating or with a particularly heavy accent (or speaking in a rushed manner, or both!). I was told off at AMS the other day for having incorrectly read back a clearance due to these very reasons! At this point we are re-defining "ICAO English"!!!
Agreed France can be particularly bad - calls in English mixed in between French transmissions in a terminal environment can make it quite challenging.