I would advise looking into very simple recipes, When I was studying abroad I was unemployed and living in a country with a higer cost of living that the UK. So I usually ate very simple meals, such as spagehetti, my Itailan friend showed me a really cheap recipe that was just Pasta, olive oil and garlic. Or even pasta egg and ham boil the pasta then thriw it in a pan with the egg and ham. cheap and tasty.
Another one was potatoes sliced up partially boiled then fryed in a wok with onions and bacon.
If times get really hard, you can simply cook some store brand instant noodles, throw some veggies in there, if you have some spare meat around that too, egg if you want, end up with a big bowl of ramen which can be very tasty.
The key is to prepare your own meals, 500g of chips will cost you about £1 but if you want chips, 3kg of potatoes will be less than £2 and you will still have over 2.5kg of potatoes for other meals. A microwavable spagheti bolognese might be 80p, but there is hardly any meat in there, spaghetti is about 40p for 500g, mince £2/3 for 500g and tin tomatoes and spices can also be aquired cheap, you can make a weeks worth of spaghetti bolognase for about 50p a meal, with larger portions to boot.
I always keep some cheap noodles in my room in case I am peckish, they are cheap and quick to make, also mozarella cheese is usually 50p a ball, and can add flavour and calories to a lot of things, great in omlettes, sanwiches and even on toast.