Napoleon also tried to stop the multiple wars and coalitions he and his French Empire had to fight once he had achieved his aims. Britain decided they didn't like that idea so they kept forming new coalitions against Napoleon and were fighting the French Empire were reasonably possible (Portugal/Spain in the Peninsular Wars).

Different century, different country, same principle. Once Churchill rallied the UK, it became a war to death with Britain having more experience at winning those wars.

Plus, the German economy would have imploded by 1941, which is why they had to start the war by 1939, conquering new territory and sacking it to keep their economy running. Britain could fight a long war, Germany couldn't.

In 1940 the UK had 2 paths ahead of them in fighting the war, slowly by trading within the British Empire and the Sterling area or quickly by buying from the USA. Buying from the USA also had the advantage of influencing the US towards helping the UK, similar to WW1. They chose the quick path, gambling that Hitler would do something stupid by 1942, such as declaring war on the Soviets or Americans.