If you are seriously interested in becoming an ATCO then the best thing to do is apply through NATS. The selection process is aimed at finding the right sort of people who will make successful ATCO's. In my humble opinion if you are unsuccessful after the second time of trying then chances are you aren't the right sort of person thats going to cut it in ATC. I'm not saying that the interviewers don't make mistakes or indeed get it wrong with some of the people they put through, but they do a pretty good job on the whole.
Aside from NATS deciding wether you are good enough or not, I think you will gain a much better understanding of the job yourself and you may decide its not for you. I'm sure there is every chance that you'll make a great ATCO and I don't want to put you off in the slightest but I would look at financing your own training as a final option.
