I thought that the switch allowed the RAF to regroup, because generally speaking the raids on london were night raids, and that the RAF only had a few pilots skilled enought to attempt night interception.
Therefore the rest(including the ground crew) had a slight reprieve, this allowed machines to be replaced, machines to be repaired, the continuation of pilot training and rotation, and the repairs to the airfields and perhaps just as importantly the buildings.
For what its worth I have always enjoyed Stephen Bungays analysis of events, He appears to have a very dry sense of humour, which may come across as condecending, and the jostling for position during the program, seemed to be mainly from the new kid on the block.