Where are my bats?

[Farplace]

For the last week I have heard and seen no sign of the pipistrels who live around here. Prior to this, I was picking them up on the detector, and generally saw them too. Am I getting my timings wrong now the nights re drawing in? There were lots of insects last night, and it was anything but cold.... but no bats. Should I be worried?
Jan

[dampflippers]

Durham Bat Group entry page

I'm not experienced enough to give an answer, but have any trees been cut down recently nearby, or anyone had a new roof/ fascias and soffits or demolished a house?
It may just be that they have a better source of food elsewhere, or are checking out hibernation spots.

[Dogghound]

I suspect that due to winter approaching they have left their summer roosts and moved to other areas for winter (lowland or sheltered areas) etc.