Munchy, I'm guessing you've been watching all those TV progs showing life on the ground in Afghanistan as it really is. If so, then you need to take off your rose tinted glasses and take a reality check.
War is hell. No amount of television or cinema or computer games can prepare you for it. You may think it looks really glamorous and you'll get loads of gongs and get on TV but the reality is far far different. I once went on a course with a Combat Medic fresh out of Afg and he was seriously screwed up. I admire your enthusiasm for the role Munches, but I'm afraid you'll have missed the boat by the time you're out of school. Our contribution to 'stabilising' and 'normalising' Afghanistan will be over by 2014 or before and the Army, in particular, will have to find another raison d'etre. I'm sure they'll still have Combat Medics but doing what I'm not sure. I can't see the UK having the appetite or the Forces to partake in any more fisticuffs for quite some time.
If you really want to make a difference to people's lives in the 'Golden Hour' can I suggest you look at the role of Paramedic. You'll get all the blood and guts and vomit, and as many fatal RTC's as you could possibly want. If it's combat you're after, then just pop along to any UK town between about 10pm and 3am, Friday and Saturday, and you'll see plenty of action.