I don't understand how anyone can call a meal without any meat/seafood a meal? (vegetarians excluded, understandably) If you do find yourself keen on something meaty go for a chicken stir fry. Sainsburys basics chicken breasts costs 5quid. That, with button mushrooms and some baby corn will cost you roughly 8quid. Serve with some rice (basics' rice is only 50p per kg) That is enough to feed three people, or two if they're very hungry.
Stir fries generally cost very little to make and are very tasty. Main ingredients: Ginger slices, minced garlic, oyster sauce, ketchup (optional), and lastly some cornstarch mixed in with cold water that you add at the end and simmer for just a minute to thicken the sauce and tenderise the meat). Season with salt and sugar. Simples