I too have just very recently went through my 3rd stage interview. The day was made up of a small group exercise in the morning and then the interview afterwards.
The interview was pretty much what I expected. To start the HR person asks you some questions eg "Can you tell me about a time when you were heavily scrutinised?". As long as your up front and honest, these questions are ok. Don't be drawn into blabbering on and on though. The HR part lasted about 25 minutes. Then the ATCO interviews you. I was given some situations and asked what I would do. The ATCO will try and make you change your answer but stick to your guns throughout. Why would they employ someone who cannot stick to their guns?
I would also say that it is very important to get in a visit or two. I visited Glasgow tower and Prestwick ACC and it gave the ATCO and myself a good talking point.
I'm still waiting to see if I have been successful so fingers crossed.
If anyone has any questions about any stage, just PM me
