I'm thirteen, and I'm writing a book. I want to try publish it. Help!?

[Louise]

It is original and way over 200 pages long. I read a lot and I think it is a good story, but I have no idea how to go about publishing it! i don't know if people would just turn me away because I'm only thirteen, but I think that would be unfair if they haven't read the book.Who says that kids can't write books too? Please help me! I live in Leeds, England if that helps anybody at all xxx