Got up to go to loo middle of night and bat flying around bathroom. Big one, wingspan noticablyt bigger than (soprano) pipistrelles. S/he flew off upstairs and seemed happy enough so opened bathroom window and left it alone. Next day had a look around house to see if still in residence and couldn't find him/her so either used bathroom window or found a good hiding place.
No idea how s/he got into the house.
Keep meaning to go out at dusk and check what types of bats flying around. In the past only has soprano and normal pipistrelles. Used to have more eg noctules but neighbour decided to illuminate ther back garden overnight and that quickly drove them away.
Ian