UK Highschool and University system?

Hi, was wondering if someone could explain this to me: In Ireland the two final years years of Secondary (Highschool) are spent studying the Leaving Certificate course, a minimum of seven subjects are studied. English, Maths and Irish (Gaelic) are compulsory and options are Geography, Art etc. The Leaving Cert is a final exam at the end of the two years and you are graded through points, the maximum being 600 points. Colleges (Universities) accept you based on your points, however the points are awarded to each College based on the popularity of that course in that College eg Celtic Studies in Trinity College Dublin may be 545 points but 355 points in Maynooth College Kildare. Also Irish Colleges (for now anyway) are free except for Entrace Fees which are about 1500E, I think. How exactly does the British system work?