It depends upon your location, finances, health, diet, lifestyle preferences and budgeting abilities.
Accomodation costs, groceries and other living expenses are quite high in London compared with many other regions of the uk.
Have you checked the amount of maintainence loan that you will be eligible for and any uni bursaries?.
But in general with combined income from: living away maintainence loan, some savings, a part time job or a regular allowance from relatives- it is usually possible for most healthy students able to budget to be able to pay for reasonable accomodation costs & groceries and still have at least £50 a month left to spend on the occasional luxury or save in case of emergencies.
Be willing to restrict spending on expensive accomodation, takeaways, restaurants, ticketed events and items that you don't really need.
Good luck!