Another top tip if going by train is to have a look in the harbour on the ferry and see what ships are in port as they will ask to see how interested you really are.
Just chill out, act yourself and look smart. Everybody else will be going through the same thing so try and relax and enjoy it and hopefully you won't need to go again.
I went 3 times ( twice for sponsership) before getting in but am now front line aircrew.