Supernick....
First thing for you to do is... NOT PANIC! Its really ok.. I did mine about a month ago.. I wore a suit and took along my CV. There were only 3 of us on my particular day as one couldn't make it. Keren Caird took us into the dedicated PILAPT suite and gave us a small pep talk about the course (obviously a bit of a sales pitch).. but I found it informative and she seemed to be very well briefed on all the aspects of the course and questions that were put to her. You then do the Maths and Physics tests which consist of 30 multiple choice questions on the computer. Make sure that you have done the sample questions on the website as a few of them come up. You have 1hr 30mins for both tests and I believe the pass mark is 70%. Time is not really a problem.. so you dont need to worry.
You then have a break for lunch before going back in for the PILAPT. This is probably the toughest part of the day IMO, but again if you just relax and read the instructions carefully you will do fine. As I recall there are 5 different sections.. but if you dont understand any of the instructions then ASK straight away. I didnt have a clue about one of them... but just took a minute to ask Keren and she was really helpful.
The good thing about this day is that you find out right away.She gives you a mini-interview (chat really!) about yourelf your family etc then if you have done ok she offers you a place on a course!! You also recieve an in depth breakdown of the PILAPT tests; and your overall performance during the session. Hang on to these as I believe they are handy to take along if you are applying to HSBC for the loan.
For my part, I am slightly older (30); came out of university about 9 years ago, and had forgotten almost all the Maths and Physics that I learned at school so I just bought some GCSE books and made sure I had a fair idea of the basics before going in and I got through ok so if I can do it.. I am sure you can too!
I am on the course on the 4th Jan; so be sure let me know how you get on. best of luck!