It's supposed to be hard, it's not easy to get through the course, probably one of the hardest mental courses for any career and with NATS if you fail your out with nothing, so the pressure is on to pass, that's why they want the best from the start. I've heard LBA are short of assistants so why not try there or if no joy just get a job at the airport and get your face known and just wait I'm sure something will crop up and LBA prefer to train their own assistants to be controllers albeit the salary is a lot lower than NATS. Good luck.