I phoned HR today to find out if the interviewer meant 10 - 15 'normal' days or 'working' days to which she replied 'working' days. She then said that I should find out early next week, but lo and behold an hour or so later I received an email from NATS giving me the good news that I have passed. Just need to do the medical, then I'm done. I know it's not final until the medical has been passed so not getting too excited just yet.
Good luck to everyone else, will let you guys know what date I have been given to start when I know them...