MjaM:
That's odd, I was told I would have my language profficency test during my course. I'm not a naitive speaker either.
How good is your english? Could it be that they want to make sure you can get ICAO level 5 (which is what NATS require)? Not sure when they would judge that though (interview I guess).
Just speculating now though, but I've been told that I will have my ICAO english test during the course (then again, that might change and I have to go there as well).