Any job/carreer ideas to do with anti terrorism/warfare/protection?

HI- I'm a 17 year old guy doing my A levels at high school. Doiong 5 AS(yr 12) levels at mo and planning to do 3.5 A-levels (yr 13). Expected to get roughly A,B,B in my A levels. I am reasonably fit/muscular for my size and am not afraid of hard work and exercise. I have become very interested in joining military teams such as S.W.A.T etc which deal with high risk operations such as anti terrorism, hostage situations etc. owever I do am not sure how to get into any of these carreers and am unsure what to take in university. (I was thinking of Law). I live in the UK but would not mind moving over to the states if i there was an oppurtunity of a more fulfilling career. I dont really want to join the bog standard military in the UK as i think i have too many qualifications (and future potential) for just being plain old infantry. I know its not the same at all (so dont give me any grief) but teams such as those featured on S.W.A.T the film and t.v series such as 24. Would appreciate any help :)