Eating cheaply is really difficult to do for the folks with the least amount of money to spend on food, as working is counter to the things that make eating cheaper: cooking your own meals, shopping or growing cheaper foodstuffs, having appliances to store items for longer periods or cook dried items, being able to plan meals out in advance, etc. That is the reason why convenience foods are popular. A lot of advice s…
From a book called Rework [1]: "When you want something bad enough, you make the time - regardless of your other obligations. The truth is most people just don't want it bad enough. Then they protect their ego with the excuse of time." I think virtually everyone in the UK has the means to eat healthy if they really want to. [1] http://www.amazon.com/Rework-Jason-Fried/dp/0307463745
Try "making time" when, for example, you've got a job where you can't bring your food with you (and would have nowhere to heat it up even if you were permitted to bring it), a long commute and a family to spend time with.
And I'm talking about a middle-class example. Now add being poor on top of that.