Why do you want to go abroad so badly? I did once too, but then I realized how limiting it would be, as in the UK, you are pretty much confined to one field. It's not a bad thing at all; it's just something that wouldn't be suitable for me.
Getting in is nearly impossible. The acceptance rate for international students is low, low, low, and your scores have not reached the rigorous standards of Cambridge. Understand that in the UK, they don't care about ECs, sports, leadership at all. Academics first, applicant second. May be exaggerating a lot here, but you get the point. You need like 2400 on the SAT and 5s on all AP exams related to your declared major for them to even consider you.
Still, I wouldn't completely discourage you from applying if it's your dream school. What do you plan on majoring in?