Advice for Sixth Form College entrant?

Hi, I have quite specific question that I really need answering. I moved from the UK to an international school in Egypt when I was ten, having done all my primary education in the UK. I'm now returning after 6/7 years and I'm going to attend a college to do my A-Levels. I have no idea about the ins and outs of a normal school in the UK, I understand British culture, but not British schools, any advice, anything would help.