Well, you should know that the fitness standard is conducted over 1.5 miles; not 2 miles. (The Americans do a 2 mile standard) At ADSC the warm up is basic. It shouldn't tire you out too much. Traditionally, you had to run it in 9:18, but according to the officer that briefed me at ADSC it has been increased to 9:40.
HOWEVER, PRAC, from what I've been told by some mates who just did it, is a hate rape on your fitness, so if you go up there sporting some weak @$$ time they will eat you alive. I've been advised that you will want to be running the 1.5 mile in under 9 min and even then you'll still need to show some true grit about you. If you pass ADSC and you're not sure about yourself, just tell your AFCO that you would like a chance to build up your strength before attending PRAC.
ADSC does determine what regiment the army thinks you are eligable for. If you don't meet para standards, they push you into your second choice, simple as.
Any other things you might need to know can be found here:
http://www.youtube.com/watch?v=lmGewhAlJ8Y
http://www.army.mod.uk/join/20084.aspx
"Beware of false knowledge; it is more dangerous than ignorance." - George Bernard Shaw