The government does expect you to top up the parental contribution to add to what's given in the student loan, that's why the student loan is on a sliding scale, with less for wealthier parents.
This is often hidden by the government, but very much expected.
Those saying get a job, it's harder than ever to get student jobs, the whole market is saturated and even supermarket jobs are hard to come by. Mine tutor and have their own online businesses, but it's hard going.
Here's the calculator:
https://www.moneysavingexpert.com/students/student-loan-parental-contribution-tool/guide/
Stop saying you are being 'used as an ATM', no you are not, you are a parent being asked for the expected contribution! I pay £300 to both children per month as that's what I can afford. Decide what you can afford, how much the other parent is paying, and then let them know; that's the amount and that's that.
You don't have to pay what they demand, but you do have to make your contribution as expected.
The whole thing is a shit show, but without parental contributions most students would have a massive shortfall now between rent, living costs and their loan, so it's not possible to do without it.