Bombings onto Britain started in July 1940. 900 German air crafts closed into Britain, 300 bombers and 600 fighters. 2662 Germans were killed along with 1250 Britains, not including civillians.
With September 19th when Hitler called in for operation sea lion which was the invading of the United Kingdom, however, this failed for Hitler.
He then called off attacks by the end of September so he could fight against Russia.
Although most of the bombs were supposed to hit the docs of planes and naval bases, they actually hit residential areas of London, Liverpool, Coventry, and other cities. In fact, one school was bombed and hundreds of students in the shelter below the building were killed.
Sources:
http://www.history.com/topics/world-war-ii/battle-of-britain
http://www.eyewitnesstohistory.com/blitz.htm
https://www.britannica.com/event/Battle-of-Britain-European-history-1940
Bailey, Ronald H., and And the Editors of Time-Life Books. World War II: Air War in Europe. Alexandria, VA: Time-Life , 1978. Print.
http://www.bbc.co.uk/history/events/germany_bombs_london