Germany abandoned “Operation Sealion”, the planned invasion of Britain, before Hitler’s decision to change the bombing of Britain from military facilities to bombing the cities. The idea of invading Britain was discarded before the Battle of Britain was near an end. However, if Germany were to defeat Britain in the Battle of Britain by some miricle, it could not have been done until at least some months after to the decision to switch bombing targets from military to civilian (Sept. 17th, 1941), and by that time, the Luftawffe had already suffered such losses that the required air support for an invasion would not have been sufficient. At that time, Germany’s only hope in getting the British out of the war with them was to get Britain to make peace with Germany so that Germany could hold France without British intervention. The planned invasion of Britain was worthless before it could begin. Thus, the invasion of Britain was impossible.
These facts do even not take into account that had Germany managed to defeat the RAF and begin an invasion of Britain by some miricle, such an operation could not have taken place less than 1 year later because of staunch British resistance, at which time the US entered the war, and would have sent not only supplies, but it’s air forces and navy to the rescue of Britain. Furthermore, Britain’s navy remained strong throught the conflict, and would have helped if not insured onw it’s own that an invasion of Britain would be a fruitless endeavour.
“On 17 September (1941), two days after the Luftwaffe’s worst day in the Battle of Britain, Hitler cancelled Operation Sealion - the name of his plan for the invasion of Britain.”
http://www.bbc.co.uk/history/war/wwtwo/battle_of_britain_05.shtml
Here is an article at the BBC that explains to you how an invasion of Britain could not have been undertaken, regardless of the decisions made by Hitler and his officers.
Enjoy!
http://www.bbc.co.uk/history/war/wwtwo/battle_of_britain_01.shtml