Hi, your question is certainly valid! My organisation runs a non-Cambridge or Trinity course (I'm the course director), but we are validated by the old head of TEFL at Trinity through his organisation IATQUO, so maybe have some right to talk on the subject.
As far as I'm concerned, once the potential candidate has proved their potential aptitude for English language teaching through their CV and application letter, followed by a possible telephone call, the most important thing is for people to be themselves and show enthusiasm, dynamism and a willingness to learn.
Don't worry too much about your interview - if you have made it this far you are probably more than half way there and as long as you don't come across as a blithering idiot you'll be ok! Teaching is as much art as science!
Sab Will, Will Power English