I did the following as a student to earn some much needed money.
8-12 hours per week of tutoring, tutored mathematics and sciences. Can be pretty good money for a relatively easy job as many parents just needed an overpriced babysitter.
I also did 6-10 hours at a pub. Just the usual bar work. If you're going to work at one, ensure that you work at one that has a restaurant type service rather than order and pick-up at bar type as tips at those places tend to be abysmal or non-existent. Also avoid working at places frequented mostly by students as tips would be scarcer than hens' teeth. If you're nice to the chef or the manager chances are you would get a free meal as part of your shift and there is a possibility that the chef might give you some food you could take home, the chef at the pub I used to work at would always give me a head of lettuce, tomatoes, sausages and at times even pieces of meat or the balance of a Sunday roast for me to take home, meant me not needing to buy it.
Weird thing I did, for my 2nd year I lived in a flat where the landlady lived below us. She told me she was renovating the flat next to mine and I simply asked if she needed any help. I told her I could help her paint and that was actually the first time I ever painted anything. Funny that from supposed to just give it a paint, she asked me to help with assembling some IKEA furniture, installed new lamps, clearing the garden and laying down new carpet. I never asked how much I was being paid to do it but when it was over she told us we could live rent-free for 12 weeks. It didn't take me all that much time, around 3 Sundays and that was it. Word does get around and if you are good chances are the word will get around fast especially if you do some work for an elderly lady.