Oh yeah, living off 12.50 a week on food relies on you being able to cook the food yourself - always buy economy and avoid ready meals - they are so bad for you and also expensive. I'm living on £15 a week, I have a pretty good diet of pasta + pesto, peas, spinach, eggs, bread, wafer thin ham, cereal, some tinned veg sometimes, lettuce. I cook myself one "big" meal a week if my budget stretches to it, like a bolognase or lasagne or all the flatmates put a quid or two in and we have a roast. Also, get yourself a fruit bowl in your room - a bunch of bananas or pack of peaches are only a quid! Also, no one else can eat those. Don't buy any crappy snack foods like crisps or chocolate except maybe a treat.
Atm I'm living off pasta, Quorn - I'm one of those cursed veggies - lots of vegetables, bread, cereal, potatoes, and then I've actually got the fruit bowl in my room already I do have a serious sweet tooth though, so I tend to buy one of those lumps of cake in Tesco for £1, and that will last me a week or so, and occasionally some ice cream, but only ever the cheapy stuff, unless the good stuff is on a seriously good offer. I should probably start baking again, thinking about it