My experience for the online test was that like mentioned by AlphaSierra, you get a sequence of letters/numbers then 5 or so more options and you have to choose the right one from it. I was scoring 23/25 on the practice goes but obviously was never told what I got in the real one.
I was emailed by NATS the following morning telling me I had passed and needed to book my Stage 1 date. The dates only went up to the end of June and I told replied saying that I wouldn't be available until July at the earliest due to final year University commitments. They replied informing me they had put my application on hold and that whenever I was ready to book, to contact them and get the ball rolling.
So I am hoping that the July dates come out soon, I shall be booking mine for Prestwick early July if possible. Good luck everyone else regardless of which stage you are at. It is truly a dream job that I have always wanted to pursue.