The turning point in the Battle of Britain, was when in response to the Allied bombing of Berlin, Hitler turned to terror bombing of civilians, instead of strategic bombing of military targets....had he stayed the course, the Brits ability to defend from invasion probably would have been eliminated, while it was tragic in terms of the civilian toll, it gave the military some breathing space to repair their infrastructure.
Well, the turning point in the Battle of Britain was the launch of Barbarossa.