The German Armed forces had no contingency plan for a rapid, opportunistic invasion of the UK. Hitler quite rightly remembered how the French had pulled themselves off the floor in 1914 (and even in 1870) and wanted to be absolutely sure that this time there would be no comeback.
the British had an untested Air defence system but the month or so's breathing space after Dunkirk was just enough to survive- up fighter production and re equip the infantry