We had a bunch of bats living out of a hole right in the corner or our bedroom window. They fly into the crack at the speed of light, I'd jump out of bed thinking I'd see them crawl into the hole, but never once did I see them. They're like mice, can shrink to half their size.
Yes, they crap & pee everywhere, it's bloody disgusting. I went around blocking every crack I could find. In the end I got fed up and declared war on 'em.
Your bats sound larger than mine were.
Have you ever seem the daily migration of flying foxes from Studley Park to around the Hawthorn/Key/Balwyn area at night. It can go on for hours, 100s of them. We sometimes stay in a Hotel in Key on the 3rd floor. We sit on the balcony facing north and just watch them fly in at dusk, absolutely silent.
https://www.youtube.com/watch?v=h3F-7iYw5iQ