Supermarkets are great BUT . . . .
Find a real butcher and go in and ask if he has some off-cuts. If he's a good one that trims his steaks etc he will have bits of meat that he may well charge virtually nothing for. Ours used to (our butcher in Spain charges me 50 cents for a 2kg bag of pork bits for the dogs! - but it's a bit of a long way for you to come).
Casserole them with lots of cheap veggies - again try a market at the end of the day as they often sell off cheaply the veg that can't be displayed any longer and it will still be good for a day or so.
Try a fishmonger too and ask him again for trimmings or fish heads. Sounds disgusting I know but if you boil them you will get some fantastic fish stock and you will find loads of good bits of fish come off the heads too. Turn into a Spanish Fish Cocido - lots of veg, chick peas and some small chunks of pasta makes for a very healthy green day stew.
Back at the butchers - if you like offal ask him if he has a lambs heart. Don't turn your nose up! Many butchers hide these away and don't sell them, but if you can find them they are usually very cheap. It is the highest quality and lowest fat meat around. Ask the butcher to remove all the yukky bits in the middle for you. Again, chop it up and casserole it or you can stuff it whole (like you would a pepper) with lots of tinned tomatoes and pasta bits.
I was a student too many years ago and, once I'd covered my travel costs, I was left me with the equivalent of about a fiver a week for food, booze and ciggies! I learnt to cook very cheaply! as I still wanted to live it up in the students union!