The Soviet Union was always Hitler and Germany's main target to begin with. It had an abundance of natural resources and arable farm land perfect for building an empire. Hitler never wanted Britain as his enemy. He quite admired the country and it's people (biggest empire in the world and all) and would have preferred if they were on his side to begin with. The main motives for conquering Western Europe were to avenge the First world war (Hitler actually made France's leaders officially surrender in the same rail car the treaty of Versailles was signed in) and to prepare for war with the USSR. Czechoslovakia for instance, had the largest weapon's factory in Europe.

By the time Hitler had reached France's Coast, plans for an invasion were put in place. Dubbed operation Sea Lion, it would have seen the Luftwaffe destroy major British military and industrial targets before a land invasion. However, the RAF and the complexities of organizing such an operation (it took two years to plan D-Day) meant that Britain seized being worth the trouble. Hitler hoped that the terror caused by the Blitz and starvation would make Britain sue for peace but he didn't account for the Japanese attack on Pearl Harbour and the subsequent declaration of war against America.

By that point, operation Barbarossa was well under way and there was no going back.