Learn to cook. Eating healthily isn't that expensive if you learn to make your own meals, you can cook in bulk and freeze to save time. Chicken breasts can be bought for £5/kilo or so frozen and are very versatile, you can make curry, stir fry, or just cook on their own and serve with rice/potatoes/quinoa/frozen mixed veg. Baked beans are also very cheap and versatile. You can batch cook a bunch of sausages or something and just have a couple with a tin of beans for a cheap and easy microwave breakfast. A good place to learn more recipes is health and fitness sites, there are quite a few with sections dedicated to cheap and healthy meals.
Edit: Holy **** just realised this thread is 8 years old, don't know why it came up in the latest section.