Standing alone in Europe in 1940-41, repelling a pre-invasion and suffering 43,000 civilian casualties in the Blitz, King and Queen staying in London to look the east end in the eye, not to mention the very British Dunkirk spirit, - we Brits see the war as an example (in the broad picture) of moral simplicity. In the grand scheme of things, we were in the right, we were the good guys. And the good guys won.
Of course there are plenty of incidents where our conduct was not morally simple, or even right, but in the grand scheme WWII allows us to feel good about ourselves - particularly since we paid such a high price compared with America, which made a lot of money. Not many wars have that kind of moral simplicity and there are plenty of examples when the British don’t have much right to feel good about themselves.
It’s easy to identify critical points - the Battle of Britain, Bletchley Park, Enigma and the Battle of the Atlantic, American entry, Soviet entry, Stalingrad, North Africa, D-Day etc. The fact is, the World War was a sum of an awful lot of parts and we should never forget any of them.
We may have lost an empire, but we gained a health service, welfare state and for a time, a more equal society.