For anyone interested, I had the experience on Monday.
I'll be honest, you know it's not real because the display isn't sharp and it's a little blurry (when you're trying to make out the runway ahead). You can see on YouTube there are some guys with FSX on the max setting and it looks amazing. The sim isn't like that, it's more what you'd expect from a computer with decent graphics.
Having said that, the interior is spot on and very good. You do get immersed in it with the screens all around and when the plane banks you do feel it bank a little, even though it's not got motion.
It's an amazing experience and it's great if you use the instruments. Because of the graphics it's difficult to land it visually (The runway is just a spot of white until you get within a few miles). I did two circuits and it was great fun and i'll never forget it. The graphics is just me being really picky.
Don't be put off if you've got the experience coming up though, it's real good fun!