I'm not a Brit but I entirely agree with @liuzhou. Before World War II, 2/3 of the food of the British Islands was imported. With the blockades, that was cut to almost zero. That was not only rationing, that was severe rationing. Girls couldn't learn to cook because they had nothing to cook. And contrary to our belief over here, rationing didn't end until 1954.
But I think the problem goes back even farther. England suffered two terrible Wars. It not only devastated the food supply, it devastated the working population. They lost almost two generations of wage earners. Now the women not only had to cook the food, they had to put it on the table. Things could never return to pre-war years.
And there's another factor that people don't take into consideration. Before, the upper classes ate well because they had good Cooks. Domestic help was no longer available and women that had never even had to boil water for their own tea were now having to learn to cook their own meals. That led to a lot of dismal failures and a lot of bad meals.
England has had centuries of history of good food. Yes, there was a period of time that it was almost impossible to get food but I would say that England has made a great recovery and that some of the old favorites never did die.
