For Germany to invade Great Britain in 1940, 1941 or 1942 it would have needed to have planned for invading Great Britain in the course of a major war. Which it hadn't.
Even if they had planned an invasion, they did not have time to convert the Reischmarine, which was essentially a coastal defence force into a navy capable of amphibious landings on a hostile shore. Before the Anglo-German naval agreement, Germany was only allowed to have 6 Panzershiffs (10000t max displacement each), 6 cruisers (6000t max), 12 destroyers (800t max) and 12 torpedo boats (200t max), no subs. Another large handicap was that they were only allowed to have 15000 men.
So not only would they have to enact an unprecedented shipbuilding program, they would have to train a whole new generation of personnel to man those newly build ships. It could not be done in less than 5 years, with the recources Germany had at it's disposal.
There's no earthly reason why the Nazis couldn't have built long range bombers with the range and bomb load to destroy RAF bases and Royal Navy capital ships and the range to reach Scapa Flow. They didn't, because they had limited resources and doing so would divert those resources from the main event, which was combat support aircraft for the fight against the USSR. And because the decision to develop those aircraft --and even longer range aircraft that could reach the United States or Siberia would have needed to have been taken in the mid 1930s.
There was one, named Herman Göring and his pet project the
Schnellbomber. In the early and mid 30's bomber development outpaced fighter developement and the general idea was that multiple engine bombers would allways outrun single engine fighters. Göring latched on to the idea like a leech and failed to see that the development of high speed fighters like the Hurricane and Spitfire invalidated the concept.
For that matter, the Germans might have been able to tunnel under the English Channel in the course of a year or two, branching out and emerging in multiple places in Kent to create a bridgehead in England. That too would require forethought and resources diverted from the USSR war.
Unlikely since it took 2 years with equipement 50 years more advanced, while digging from 2 sides simultanious. It would also assume a quick victory against France, which even the most optimistic Wehrmacht general did not see even as late as '39. And lastly the amounts of excavated dirt would provide for a visual clue for what they were doing.
The fact of the matter is that Hitler was totally surprised, dismayed and nonplussed at continued British resistance after the fall of France. That was simply not supposed to happen. Not with the Cliveden Set sympathetic to the Nazi Cause in the UK. Not with the Nazis offering the UK liberal terms including keeping the British Empire if only it would stay out of the European continent and Russia which was none of Great Britain's business anyway. The Conservative Government was supposed to fall and a new British Government was supposed to negotiate an armistice wih Germany. Instead, Germany got Churchill and what was apparently mindless defiance--after the Germans even allowed the British Expeditionary Force to go home minus it's equipment at Dunkirk instead of cutting it off from evacuation by sea, which the Germans could have done.
Except that the Nazis never offered any terms. Hoping your opponent would just roll over and surrender isn't mindless defiance of the UK, its clueless optimism of the Nazis. Hitler hoped the UK would acquiesce Nazi dominance of the continent, while limiting itself as a global naval empire. He failed to see the value attributed to treaty commitment which made for 2 very large blindspots:
1) Any peace agreement made, would have little value since Hitler allready proved he violated them at whim
2) A peace agreement under those terms would be seen as a British betrayal of it's allies for it's own self-preservation, something that could cause a landslide in Commonwealth and diplomatic relations.