I also found a site that says "a great number of lighthouses were demolished during the 1939-45 war as it was considered that they might act as a navigational aid to enemy shipping and aircraft". This would imply that generally speaking they were turned off.
Nemo
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"I'm afraid there is no disguising the fact that King's obsession with the Pacific and the Battle of Washington cost us dear in the Battle of the Atlantic".
Sir John Slessor GCB, DSO, MC, DL
AOC-in-C Coastal Command RAF
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