The defense seemed to obtain lesser results than in the first period, probably due to the shift to night operations.
On the other hand no air force has ever switched to night operations because its day missions were going well, has it?
Britain's night defences certainly had a long way to go in 1940 but in early 1941 the RAF's night fighters were dramatically improving their kill totals, month-by-month. What's surprising is that British night defence systems were developed rapidly in 1916–18 but received so little attention in the run-up to the Second World War.