You get a tuition fee loan and a maintenance loan (for living costs) from the Student Loan Company. The tuition fees get paid straight to your uni and the maintenance goes straight into your bank account. If you can possibly avoid it, don't get a normal loan from a bank as the money you borrow will accrue interest meaning you'll pay back a hell of a lot more than you borrowed, over what will probably be a really long time. The SLC allows you to borrow your money, keep it til you're earning over £15,000 pa then pay back the exact amount borrowed, no matter how long you've kept it, with no interest.
It's a good idea to earn as much as you can in the holidays, especially if your parents can't help you out with rent, as the accommodation companies for the RVC especially will rape you something chronic. Unite housing really is daylight robbery, a total rip off, and everything costs more in London anyway. My two best friends are in Mary Brancker, where the rent for the year exceeds the amount the SLC will actually give you by £900; one's parents are paying for her accommodation but struggling, the other has given her entire loan to her parents so that together with their £900 contribution they can pay the rent, then lives off her own earnings during term time. So you can see that if you have to use some or all of your loan to pay for accommodation, you really will be pretty strapped for cash! Depending on how much your parents earn there are bursaries and grants available so if you're at the lower end of the income spectrum make sure you look into those as well.