In message , Sacha
writes
Am I seeing things? The evening is very chilly but I'm almost certain I've
just seen a bat fly past my window! Can anyone tell me what time of year
they usually get going - I associate them with much warmer evenings than
this.

Could be. I haven't seen any so far this year but last year I spotted
the first of our regular Pipistrelles over the garden (a bit nearer the
coast than you) on 3 April.

--
Robert