I heard a rumour that all of the APP course at one of the colleges were already employed or otherwise spoken for. Some ANSPs have been approaching succesful ADI students as the supply of APP qualified students are snatched early.
Make sure you are confident in your ability however. Some of the colleges offer a short aptitude test, the cost of which may be refunded on arranging a subsequent ADI course.
I am not an employee of any of the colleges; I have been in your position a number of years ago but still managed to get qualified.
The NATS of 2009 certainly isn't the employer it once was. You can still have a fulfilling career outside of their system anyway.