Ignition Override,
Nonsense!
The fact that X-Gerat beams were intersecting over Coventry was detected by 3pm that afternoon. Ultra intercepts revealed that a major attack on a UK target was planned but there was some uncertainty over the code names used. Churchill was infomed that afternoon an attack was expected on london that evening, he was on his way to Chequers at the time and turned round and went back to London.
Even if it was known for certain that the target was definetely Coventry there was precious little that could have been done in the time available. Night defences were pitifully inadequate at the time and almost totally ineffective.
To link Coventry in November 1940 and Dresden in February 1945 shows you have no understanding of WW2!