I just wore white adidas trackies, blue nike trainers, a black puffer jacket and a red adidas cap and left my 2 big sleepers in my ear.... dont worry mate but I did tuck my gold medallion on my chain under my coat so make sure you dont go with a medallion out!!
I just wore normal clothes, everyone else there was in jeans and t-shirt, apart from one guy going for RFA, who turned up late wearing a suit, but I think he had just come staright from work. Just wear whatever you feel comfortable in.
I wore a suit, and so did a couple of other lads. I felt like it was a bit unnecessary being all dressed up. But then at the end I was taken to a room with another lad to be told we'd passed. He was dressed pretty smart, so I'm glad I hadn't come in every-day clothes.
Conclusion: it really can't hurt, in the slightest, to be the smartest chap there.