I recall there being a thread talking about how the British stereotype of bad food came about from the privations of WWI and WWII--prior to WWI, there was a very rich food culture. However, Reddit has terrible internal search functions, so I'm not able to find it. Could some enterprising British culinary historian point me in the right direction about historical British food?
I'm not sure I agree with the premise of your question, that the stereotype of bad British food comes from rationing during the two World Wars; my understanding is that's older than that, and although I haven't studied this particular aspect of British food history, my instinct is that it's much more to do with the changes to Britain's food supply system and food culture in the nineteenth century. I'm afraid I don't have a lot of time to elaborate at the moment though. I'll try to come back with more later.