Food is cheap in the UK relative to earnings. I have lived in a few other European countries and prices there are much higher.
What is different in the UK are expectations and food habits, as well an an innate unwillingness to use up leftovers in creative ways.
Soup and maybe bread are a normal meal in many countries - both for lunches and dinners. They are dirt cheap to make: meat stock from bones and salt, vegetable stock from offcuts (such as the ends of carrots and swede that no one eats), fish stock from fish bones and heads. Throw in a few vegetables past their best before date and some soup noodles. Or blend whatever vegetables with leftover poatoes or mash to make a thicker soup. They freeze well and make several portions - I eat homemade soup every day at work and it's considered odd by some of my colleagues, who moan at the cost of food but buy a meal deal every day.
Stews and pies are are a great, cheap way of cooking with offal, which is a fraction of the price of muscle meat. Speaking of offal, cooking with liver, heart or black sausage is a good way to get cheap nutrition. Again, considered perfectly normal elsewhere but the look of disgust on so many people in my social circle when I mention that is priceless.
Then there is seasonal food. You just don't buy fresh fruit, salad leaves and herbs in winter, you either grow your own on a windowsill, which is very easy to do, or you buy frozen or canned. Buy winter vegetables in winter, summer ones in summer and adapt your meals around that.
And leftovers are made into omelettes, potato-based cakes and pies or otherwise incorporated into another meal.
The whole animal, the whole fruit or vegetable are no longer considered as bases for different foods and only prime cuts are deemed acceptable for meal times. See also wonky fruit and veg - why is that even a thing and not thrown in with general fruit and veg? Because people wouldn't buy it, but why?
TL;DR, I find that a lot of people in this country are not using foods in a way to get the most out of them.