Ab-initio ATCO are sent to UK school during initial training in order to improve English
I knew this already but it's difficult to tell when you talk to them.
As a matter of interest have you, as an ATCO, sat on a flight deck from the south of France to the north of Europe (or the other way around) and don't feel a touch of embarrassment when you hear your french colleagues control aircraft in english and compare their command of this language to that of your Swiss, German, Belgian, Dutch and Scandinavian counterparts. I would gladly invite you to sit on my jumpseat so you can hear it for yourself, mon cher ami aiguilleur du ciel.
That's what this thread is all about. Get your act in order, be as efficient and fluent as your northern european colleagues, and people will stop having digs at you.