Mark,
I passed my PRMC September 01. So have quite a good idea of what sort of level you need to be at. I am now in phase 2 of training & will hopefully get my Green lid in March. All the advice above is very relavent\helpful for what you need. Doing a lot of sprint\speed work is very important, as you need the strength in your legs. A major part of your PRMC will be on the bottom field (Assault course) & this is where you will need some of this leg strength.
The best advice I can give you is when your having a down day, try & push yourself more than usual, as this is what will be expected of you.
& when your down on your course, don't give up on anything, even if your hanging out your ar**. Stay switched on, all the time & be a team player when they give you tasks.
Hows your pressups, chinups etc?
Best of luck.