You really are not going to go to a central University welfare department to complain about an inconsiderate flatmate
I agree, this is a serious problem. And, in many universities, more and more of the "university" accommodation is actually at arms length, and the landlord isn't actually the university anyway. And university accommodation is, outside a very small number of older universities, only really available to first years, with almost all second and subsequent year students living in private accommodation.
But again, I'm sorry, this is where money and social capital arises. Parents engage with landlords. And in some cases I know of, parents simply enable their children to change accommodation, up to and including swallowing the price of breaking the lease (or being more willing to say "sue us for it, then"). The flip-side of housing which is not owned by the university is that the university can't withhold a degree because of money owing to a private landlord.
My guess is that DDs University has a higher drop out rate than Oxbridge
Pretty much everywhere has a higher drop-out rate than Oxbridge. The reasons for that are complex and tricky to unpack. It's hard to plot a robust scatter-graph of drop-out versus background because we don't have good data (Polar et al aren't great) and because drop-out rates are low enough that there's a lot of statistical noise. But I would bet a large round of drinks for an entire seminar group that dropout rates are massively inversely correlated with parental support, and the better you measure that support, the stronger will be the effect.