Hello mpplp,
I can't answer all your questions but I'll have a shot.
1) Yes, I'd consider a suit absolutely necessary. You are trying to convey a professional image, you'll not do that in a pair of jeans and a t-shirt.
2) I doubt you'll be expected to know the data inside out but any information they have sent you is fair game for questioning. Try your best to learn it all because if you get through, you'll have to learn it all for the college anyway! It's been a few years since I had my interview but I was asked things like typical cruising levels, speeds, passenger capacity, type of engines etc. They also showed me pictures of aircraft which I had to identify and give some info on.
3) I'm not too sure. With bigger courses than before (I believe up to 60 on a course now
) I suppose the chance of getting to the college will be a bit better than usual.
4)It depends. The process is much quicker now so could be anything from a week to a month.
5) I think the starting pay is £10k all in.
6) If you do area or approach you will most likely get posted to Swanwick but the other centres are a possibility. If you get aerodrome it'll most likely be one of the London airports but could be anywhere.
Hope that helps.