I flew in and out of CDG regularly last year and found the French controller's ability to switch from French to English without skipping a beat quite astounding! Although speaking English for over 30 years and having done all my flight training in English, I am a native French speaker and I did struggle in French airspace and on the ground to picture what was going on around me! Purely because the "trigger" words are not there. However, must say my experience of the French controllers was all positive, dunno how they do it!!!!