Brian81 is right regarding the licence.
ANO Art.92 (1) (b)
The CAA shall not grant:
(i) a student air traffic controller's licence to any person under the age of 18 years;
or
(ii) an air traffic controller's licence to any person under the age of 20 years.
But bear in mind that your course (by the time you get on it!) lasts for about 18 months, and the time it takes to get your first validation, you're going to be at least 20. So, don't worry about the age. As "sla" says, just concentrate on being confident in your ability.
Good luck with your interview. I have mine a week Friday!
Take care