Info on boarding schools in the UK for overseas students?

I am thinking about going to boarding school there in year 9 ( I would need a scholarship though.. But i think i'm pretty bright :/ i think...) I want to go to cambridge uni for my undergrads. I need a student visa right? ( i am not a citizen in any of the countries in the eu or commonwealth). Do i need a permanent resident? How do I apply for one? What are some good boarding schools? Any suggestions? I've been looking for one in the cambridge area and came across a school called the leys.. Is the school good overall?