Large Bat

Observation - Large Bat. Description: We have a large summer nursery colony of Pipestrelles in our house loft (160+), which hibernate elsewhere in the winter. Some days ago I observed what I at first thought was a Woodcock (to give an idea of relative size)circling a chimney of the house but

We have a large summer nursery colony of Pipestrelles in our house loft (160+), which hibernate elsewhere in the winter. Some days ago I observed what I at first thought was a Woodcock (to give an idea of relative size)circling a chimney of the house but then realised it was a bat; it was not flying fast at all. I saw it settle on the wall and crawl below a coping - have not been able to locate it inside the loft. Given location does anyone have an idea of how to narrow down particular species. In the summer I occasionally observe large bats flying high well above tree height at dusk but they seem to be travelling not feeding and are soon gone.