I managed to survive my first year of university life without getting a job, i had no financial support from my parents, i just had the full amount of student finance and a 500 overdraft. Managing my costs was ok for the most part, i would recommend trying to gather as many resources for your course as possible before starting university, as books alone can be an unexpected expense. Food around uni is alright, can be a bit costly depending on what you want to get but i advise tescos for lunch or a packed lunch for the majority of the days you are in :)
the local pubs and bars are always looking for part time workers, and if you plan to stay in Cambridge over the holidays you will get more opportunities available to you as employers like to know who they can rely on, most of the city centre is a short walk (20-30mins) away from the campus and there are loads of shops to cater for every shopaholics secret desires.
and the night clubs are again only a short walk away from most of the accommodation available, making it far easier to walk or in my case stumble home