Thanks for the advice everyone!
Nudelkopf: I don't have a stable job. However, I do high school tutoring, have one student who I am getting $70/w from, and can get more (although additional students are more likely to bring in ~$30/w each). I'm also likely to get a tutoring job at the uni next semester which would be about $120/w, and if I do, it's likely that I will keep it. In addition, I get a $6500 pa scholarship from the uni, and $5000 pa from parents. My impression is that PhDs in the US come with scholarships almost automatically, but they are more stingy in the UK. I expect to be able to get a scholarship somewhere, but it's hard to be sure.
Upon reflection, it is probably a good idea to keep the money somewhere more liquid. I should be able to start a Vanguard account, but I would only be able to withdraw $2000 from it, which might not be enough. This makes term deposits and high-interest accounts look good. Does anyone have any advice on good accounts?