P Wilson,
It sounds like you've got the enthusiasm that's needed and a good level of background knowledge.
The first stage is not an interview, just a series of tests. Try and absorb anything you can about ATC and aviation and do try and go back through the thread...lots of valuable stuff in here.
I was a 'super-wannabe' when I applied back in 1997. I was an 'anorak' if you will, devouring anything and everything to do with aviation, although I never got into reggie spotting. I assumed that everyone who got accepted on to the course at Bournemouth would be like me. It was a shock when I found out there were only two or three of us on a course of 36, and a handful of 'lesser geeks' who could tell an A330 from a 767.
Other than that they were all aviation virigns. Not that that prevented any of them becoming good controllers. The skills, personalities and characteristics are more important than knowledge.