Relax!!!
You've been asked every question multiple times during your training. If you've done the work, it won't be an unpleasant experience. Think of it as a chance to show that you are taking your new career seriously.
Make sure that you are 100% on PTS (don't want to make yourself look like an idiot for not knowing basic stuff), and also on Train Protection.
Work with the others on your course. Test, support and encourage each other. That's what the Railway is about.
Good Luck!