Are you a UK student? Undergrad or postgrad?
I was in the same position (I actually was contributing money to my household bills to keep us afloat!) and here's my experience. If you're a UK undergrad, you should be able to get Student Finance to cover your tuition fees and some of your living costs. I was in the highest bracket for SFE entitlement, so I got the maximum amount for the maintenance loan which was about £9k a year. On top of that, at Oxford at least, there are two bursaries for undergrads (Crankstart and a general Oxford one - you can only choose one), from which I got a few extra thousand a year. You're allowed to work during the holidays, which I did, and because the Oxford terms are so short that means you have about 5 months in the year where you're not in the city studying. If you work during those you can get a few extra thousand as well. The careers service at Oxford is very good, and you can get funded internships depending on what field you're in. It was some work, and it's not like I could just spend on whatever I wanted all the time, but it was certainly doable and I lived fine to be honest. I imagine Cambridge is quite similar.
And if you ever fall into severe hardship, there are hardship funds at most, if not all, colleges that you can turn to for help.