Seems I'm quite late replying to this one, but I've only just seen the thread from the newsletter!
I lived in the UK until about December last year, and am a keen cook who is used to usually having a next-to-nothing budget myself! I'd would advise the following which helped me:
1) I'm assuming you're in the UK here by the way as this is a UK site, but the topmost one would be to avoid supermarkets. I did to try and avoid the pesticides and E numbers etc. in my food and never looked back. I know it's hard nowadays, but if you hunt around you may well find a grocers, a close by farm shop ([or farm in general who'll be happy to sell to you] - don't worry about needing to bend down or pick the veg as they'll have done this and will carry it to a car for you if you do drive), or sometimes there are local cornershops, which, if run by Indians sometimes provide a veg store. I found all of these, especially the first 2 far cheaper on a weekly run than the supermarket, and I like to think a bit healthier too. As the next step suggests, root veg is a best buy and can be made to go a long way.
I'd like to argue with the above too
I'd say AVOID BOGOF offers and everything of the sort. Supermarkets thrive on distracting people - placing more expensive items at eye level, littering the store with offers and tons of other tricks like this in order to get people to spend more in their stores. If you have to shop at a supermarket, write a list beforehand, and stick to it. Never shop when you're hungry, and always check the shelves for the cheapest (but healthiest - no good buying a tin of tomatoes if it's just 1 tomato in a ton of water and sugar) products and keep your hard earned money yourself rather than letting them have it. You can do what I did and see why I'm suggesting this - go for a normal shop, taking advantage of anything that looks tasty or is on offer & keep the receipt, then on the next shop, use this method and see the immense price and healthiness difference!
2) I used to cook on a Sunday a big batch. Soup has already been suggested as one cheap option but I used to do either stews (which use non-tender, cheap cuts of meat and can be left to cook), or mince dishes (lasagne, shepherd's pie etc.) a lot. You can put a ton of cheap, cubed root vegetables like swede, carrot, parsnip, etc. in (ok maybe not too many potatoes if the carbs aren't that good for diabetics) not only will all these veg bulk up a soup, stew or mince dish to make the pennies go further, but they'll make you fuller/need less of the meal, and also they're healthy. These I'd cut into small portions and put in the freezer to have over the coming weeks. They go quite a long way, and if you're better-willed than I am, keeping to the sliced "normal-person" portions will help watch the calories, though I could never manage to have just the one portion myself! :wink:
Having said that, I used to do that more in winter (well apart from the soups). I guess you could start looking at both salads which would be a cheap, healthy option now, or making quiches/flans which again are a one off cost, bit of cooking effort but which could then last in the fridge (under cling film) for a few days food.