Cost of Living
One word: Expensive. This is mainly due to the high exchange rates. As a rule of thumb, you can expect to see the same numerical price for things in both places, but in Cambridge, those prices are in pounds, whereas in Boston they're in dollars. Because a pound is worth more than a dollar, things are more expensive in Cambridge than in Boston. You can expect to spend £5 - £10 for lunch and £10 - £20 for dinner at a restaurant.
Banking
You will need a UK bank account to register for a cell phone plan and make online purchases. Setting up an account is easy but the activation period is 2-5 days. Head to the bank as soon as you can to register because the lines get really long once all the other freshers arrive. One of the best things about the UK is that you can use other banks' ATMs without fees! So there are no wrong choices.
You will need a letter from your college and your passport to register for an account. Ask whatever college administrator is communicating with you during the summer to produce the letter for you.
Campus Jobs
Students are discouraged from having jobs during the school year. The few available jobs are working in the library, at the college bar or at May Balls. You should receive emails about how to apply for these positions or ask around.