You might also want to look into not staying in the UK, if they aren't interested in you as a grad student. I don't know anything about the difficulties involved with that, however.
Don't forget to work hard with established professors as an undergrad in order to get the letters of reference you'll want for post-undergrad education. Get amazing grades. Learn your subjects backwards and forwards.
Getting people to bet on providing you with more education is a two step process. First, you have to be damn smart and hard working. Second, damn smart people have to know you are damn smart and hard working, and want to champion you. Or you could rely on luck.
