My experience at university was very much that most student did primarily live off their loans, plus the overdraft, which they worked off in the summer.
The maintenance loan was £3500, halls rent at the time was £2300 for 40 weeks. £1200 plus £1000 overdraft gave £60 a week. In a cheap, northern city, that wasn't actually bad for living expenses (since all bills were included in the rent). You could get wasted for £10 in certain clubs, and a huge pizza was a fiver. Parents did tend to top up a little, but it tended to take the form of occasional £2-300 top ups than a regular fixed amount. Summer jobs would refill the overdraft, and allow for a further top up.
Caveat - I largely knew arts students. The library would supply most resources, J-Store the rest.
It sounds quite ridiculous coming from that background that students would need huge parental contributions.
In part, i will be out of touch with living expenses, but at the same time, I have seen threads on here where parents agonise about spending extra on a studio flat or an ensuite double room for a student, and fret about them buying nice clothes and decent food. Which is very, VERY far from student life as I remember, and doesn't sound at all fun!