'What....is going on up there!!??'

A pair of squabbling Sparrows has it turned out...which weren't squabbling for long when they realised this one was looking up at them :-)

Regarding the Blue Tits, their visits are infrequent - literally blink and you will miss them most times, with the extra showing evidence that they (I've seen one pecking at it) are pecking more and more at the entrance hole, and the area immediately surrounding it. The wood is cedar.