My scholarship definitely came later, like a couple months later. That sad, I'd assume each funding body (I.e. the Clarendon, HEFCE, college specific funds, department specific funds, etc) may have different dates.
As for living costs, as I remember it my funding was about 13k for living expenses, and I lived in some of pricier St Ant's accommodations (Founder's) for 10 months (technically I was in another building for the summer though). On the day I left and closed my bank account, I had exactly 82p left in there, which means I spent pretty much 1300 pm. But I did buy a laptop with that money and I wasn't scrimping or saving. So you could do it for less, if you live in some of the smaller rooms, or live off campus farther from town and bike to campus for example.