<<I'm a former NATS trainee and was axed after failing>>
OK, so you have failed. What reasons did they give for failing you? Was it practical, oral, written?? To fail the last two would be unforgiveable but a practical failure suggests that the student may not be up to the job - and that's not meant as a criticism. Lots of people want to be controllers but many simply do not have the peculiar skills required, even though they know the books inside out. On the other hand, I've seen a few really good practical controllers fail to validate on the oral board.
I went down a similar road many years ago and it didn't take long for me to realise that it's nigh on impossible to DIY. I think your only option would be one of the private colleges but it will cost you an arm and two legs and you won't be guaranteed a job at the end.