intertia,
I've heard nothing from NATS since my Stage 2 on 4th December however I was not confident in my performance, making some silly mistakes in DART really let me down.
However, the 15 days is actually 15 working days. So don't be surprised if you have not received results by this Wednesday (19th), it will be 10 working days since we took the tests tomorrow. Our 14th working day is Christmas Eve so we may not get our results till post-Christmas maybe even New Year, I guess it just depends on when HR are working.
Goodluck anyway!