Might be a bit off topic as it's not strictly caving related, but I'm sure some cavers might be interested in the arson of a lesser horseshoe roost  . I was surprised that they intend to replace the building - are bats likely to return even after the old one was destroyed?

Yes

I'm not sure but given that frogs return to where a pond used to be (at least they did in our garden) it's not improbable.
I suspect that any appropriate site would be visited by bats looking for a roost.