Anyone serious about living on little should read http://www.theskintfoodie.com/recipes.html

And if you're really serious about living on less than that then I can only recommend Orwell's "Down and Out in Paris and London" for the wonderful tip of smearing garlic on a knife before you put butter on bread to convince your body you've eaten a hearty meal.

I personally lived a couple of years on http://www.complan.com which is about as close to Soylent as you get when you're homeless and broke in 1994 and holding on to the hope that it might stave off whatever the next illness is going to be.

My personal tip: Stale bread, old tomatoes, old cheese = pizza for less than 20p.