You've got until next September to save up, and starting off with even a small amount in the bank will help. Apart from that, getting an overdraft and a part time job/job in the holidays is about all you can do.
You should discuss with your parents whether they can help you out a small amount though; explain that the system works on the presumption that they will help you out and the fact that they won't doesn't make a blind bit of difference. They're the reason that you get so little; that might not be fair on you or them, but they can hardly want you to starve. Perhaps discuss with them that you won't after all be living at home and incurring costs there, they could maybe contribute to covering your food costs (even if it was say only £20 a week?)
It's not true no one's basic loan covers their rent though; it very much depends on where you study, and the living costs of your choice of uni is something you should take into consideration at least a little bit before you apply.
My loan covers my rent, and gives me £530 left over for the year-so about £170 a term-(and yes, it is the minimum £3564) which isn't a lot, but has been helpful. The cost was part of the reason why I went for Cardiff over a few other choices; I knew before hand it was going to have to be an important factor.