Hitler's Greatest Mistake Was Invading The Soviet Union.
Indeed, Hitler should have made nice with the Soviets and instead, he should have staged a massive invasion of the British Isles. If that had happened, one can be quite sure that the UK would have an almost one hundred percent White population.
It is quite possible that if every UK soldier who died in the second world war, had been suddenly, together as a group transported in time to see the future of their once great nation would if they had the opportunity to return to their relative present, would join forces with the Nazis.
Although that scenario would most likely fail too since the Nazis had already kicked off the whole Invasion of the Soviet Union thing. Plus the Nazi's wouldn't believe in time travelling Brits anyhow and they would have been shot, imprisoned or committed. Just saying.