Hi Marco,
Out of interest, when was your Stage 3? I really believe that everyone's Stage 3 is different - in mine we did spend a good bit of time on the HR stuff, but perhaps because of my age and past education/employment experience, we didn't spend that much time discussing my skills.
However, I must have spent at least 30-40 minutes going through technical stuff (beginning with an ATC scenario, and following on to things to do with a tower visit I had made) in great detail which I was pushed hard on and challenged continuously. I don't have a PPL/ATPL or any other type of aviation background (I'm a scientist by trade) but I was still asked loads of technical stuff.
Advice to others: Although there is a list of questions that the interviewers can choose from, especially for the HR stuff, what you say in return will dictate what the interview is like and where it goes from there. Everyone is different, and therefore everyone's interview will be different. Be unprepared for either the HR or the technical stuff, and you may find the interview more difficult than you'd like. If they don't ask you everything you've prepared, consider yourself well prepared for the interview, and that maybe you've saved yourself a bit of learning for when you get to college - it's not a bad thing, and definitely not time wasted!