D'Artagnan,
I agree with Moira.....
... if you find the accents in the sample test difficult to understand, you just don't want to hear the real thing ...
I just took the sample test out of pure curiosity (no, I'm not an air traffic controller).
Looking at the results afterwards I didn't do badly at all.
My problem was simply assessing the scenario as a near-outsider, and typing in the right answers fast enough !
At no time did I have any problem with the accents... which might raise questions about how realistic the test is.