Skyslater
I failed stage 3 last year and i got feedback from them, but it does take a while. I got the same response about needing to wait 2 weeks - it is becuase the interview notes go off to a third party to be verified, and then they are returned to NATS HR to deal with and file away (i guess) I did have to wait a good few weeks but they did get back to me.
It is definitely worth pursuing, especially if you are going to try again, as the points they give you are very handy. Be sure to have a pen/paper handy when they call back as she will give you lots of info. Or she was kind enough to give me her mobile number and i called her back when i had 15-20mins free to talk properly.
She also let me know that i wasn't "barking up the wrong tree" and it was worth me trying again, which is nice to know !!!
Good luck with it and do make sure you get the info you want.