It's actually not that complicated (you should see the US system...). It's really split into two areas, loans and grants.
You are eligible for two loans. The tution fee loan that covers the full £9000 tuition fee (for the duration of your course) and the maintenance loan that covers basic living expenses (such as accomodation). The latter varies in amount depending on where you are studying and how much income your parents make. From what I understand, students in London are eligible for more money. When you apply through Student Finance, the system will automatically determine how much of the maintenance loan you are eligible for.
The second is maintenance grants. Depending on your parents income, you are given money that you do not have to pay back. However I should stress, you are only eligible for grants if your parents are earning very little money. I advise you look at the Student Finance site for exact figures. Like the maintenance loan, this goes toward your living expenses.