In my experience, the average British person has no idea how to cook a square healthy meal that is also appetising enough for them to choose it over other easier options. Cooking is taught poorly (if at all) in schools and at home.
This isn't about money. We have 64% of the adult population overweight and obese, 22% at age 5, and 37% at age 10. All those numbers are growing.
The excuse often brought up is that it's "expensive to eat healthy". Absolute bollocks. It's far more expensive to eat ready-meals, order takeaway, and dine out than to buy ingredients and cook.
For snacks, a banana costs £0.15 and fills you up for longer than a £1.00 chocolate bar. But people want the chocolate bar!
I've lived in a city centre apartment block for the last few years. The frequency with which I've seen the people around me having McDonalds, burgers, pizzas, and other oily, salty, high fat, high calorie food delivered shocks me. For some people, it's upwards of 5 times a week!
If you go to a "local" or "express" supermarket, microwavable ready meals and junk food represent most of the aisles, and when you take a glance at the shopper next to you, they are buying mostly junk and inconvenience food.
If you go to a supermarket after school closing time, you'll see tens/hundreds of kids buying energy drinks (despite the age limit), multipacks of chocolates, biscuits, sweets, crisps, 1 litre bottles of pop. Evidently, they have the money for it (from their parents). University students across the country keep fast food and takeaways in business via their student loans and grants.
When people here do cook, it's:-
1) Stir fry
2) Spaghetti Bolognese
3) Pasta and sauce dish
4) Something on toast/jacket potato
Every meal that gets microwaved in my office for lunch is one of these 4 things. Basically just throwing a bunch of stuff in a wok and mixing for 10 minutes.
This is of course all anecdotal, but it's plain as day that it's about personal choice for many people, and not money. Our country has a serious problem with food and alcohol addiction, and an extreme aversion to exercise. Most people would wipe out their life savings/all of their income to eat slop as much as possible, at the detriment to their finances and health.
Every stage of British life, from infanthood, primary and high school, to university and beyond prepare the population for gorging on high energy, salty, oily junk food.
We will easily hit 75% overweight/obesity by the end of the decade.