How to cut the cost of your food:
1) always buy the cheapest variant the cheapest possible shop has - try Poundland, B&M Bargains, Home Bargains(?), Street markets.
2) Hang around markets at the end of the afternoon and buy vegetables by the sack at give away prices at the end of the day. Look at what tinned and packaged food is available on market stalls, ignore consume by dates.
3) Find out when your local supermarkets, mark food down and haunt those aisles, sections and gondolas when that happens.
4) Forage: pick wild provender, herbs fruit (blackberries, apples, greengages, sloes,. Do a foraging course so you know how to recognise, gather and cook food for free.
OR, since you can afford a reasonable diet.
1) Plan a weekly menu, use recipes you know and ones available online
2) Use recipes based on cheaper vegetables and fruit, root veg, cabbages and apples, not Butternut squash, sweet potato, raspberries, or mangoes.
3) By own brands not 'branded' brands
4) keep an eye open for special offers, buy food and veg on its sell by date and of you cannot eat it immediately cook it and freeze it.
5) At the end of each week, survey what fresh food is still in the house and then start the next week's menu plan with dishes using those ingredients, or make soup and freeze.
6) portion control. Serve food away from the table and give no-one anymore than they can eat, so that only empty plates come away from the table.
7) Nil food waste. No edible food ever to be thrown away, only vegetable peels and trimmings and that to go on a compost heap so that it can help you.....
8) Grow your own, even if it is just herbs in a window box.
9) Do not eat between meals
10 Do not buy any processed foods that you can make yourself.