Just to confirm that dd1 has just under £100 a week, but spends more like £70 (self catering, cheap small bedroom / non en-suite). She has very cheap hobbies, a free bus pass from the university hall, free railcard via student bank account, and she doesn't drink / club, so is saving any left over money for the year abroad as we have no idea how much that will cost. Some students have way more disposable income and others have less (depends on family circumstances).
The main pinch point seems to come when the landlord needs a deposit for the 2nd year accommodation (in dd1's case this is four instalments of £1400 each - first one spring /summer of year one, second one autumn of year 2 and so on ) so if you can plan ahead you won't such a panic. This is the item that has caused the biggest problem to financially stretched students in year one.
Obviously it will be different at other universities, but this might help as a guide.