Let me be clear, you are talking nonsense. Both about an invasion of the UK and the power of Britain and the British empire.
What is the basis for your argument? The Germans had no problem in overrunning Poland, Denmark, Norway, Belgium, Holland, Luxemburg, France, North Africa, Yugoslavia, and much of the USSR (until the winter snow set in)-—why do you think England would have been spared a similar fate had it not been island protected by the English Channel from the rest of Europe?