If you want good quality food, i think that it is worth spending the money on good food, making the absolute most out of it, and then make savings elsewhere.
WE get an organice veg box every week, and and organic meat box once a fortmight - it works out about the same price as buying organic from Sainsburys.
BUT, we get a slightly larger box than we 'need', paying a couple of pounds more, which means that we make loads of use of leftovers. We make soups the day before our next box is due - only takes minutes and they are great for lunches/lazy meals, and freeze well.
We always make our own chicken stock, which takes as long as it takes to peel and onion and a carrot and fill a pan with water.
Getting a 'bit too much' for the weekly shop means we always have a well stocked freezer; we can never justify take aways due to lack of anything in, and...this is the best bit...we hardly ever go to the supermarket anymore. I do an online shop about once a month now for household goods and 'staples' like rice and pasta, and fritter so much less away on unnecessary stuff.
Also, we find that every now and then, we can cancel that week's meat and veg delivery altogether.
WE have been really amazed at the reduced cost of food, since we have started this, and I would recommend anyone giving it a try.