My parents have to give me some money each month because the Student Finance I get isn't really enough. I'm a first year in catered accommodation (which I like), but it is quite expensive for the year (over £6,500), and at my university the prices are going up each year (£7,000+ next year). I definitely needed extra money for things like books for my course, some of which were quite expensive. Plus my university is collegiate and I didn't expect to have to pay extra things when I got there like JCR memberships to take part in events! But luckily next year I'll be in private accommodation in a rented house, so I'll hopefully have a bit more control as to how much I want to spend in terms of food (rather than being forced with one amount as I am now with catered accommodation).
However it depends how much loan you get - I know people who get over £9,000 (I think they received bursaries from the university on top of their Student Finance loans) and considering the accommodation price, they don't struggle and have some money left over. Some of them have saved the money rather than just buying expensive stuff, which is probably a sensible option.