Probably more stalking than resting.
Brazel Street woodland.
We were a bit excited but sad for the little Blue-banded bee. We've never seen cuckoo bees in our nearby garden despite the presence of many bbbs.
I think they are both just roosting. I don't know of any evidence that Blue-banded Bees recognise the Cuckoo Bees as a threat unless they are in or near the nest hole, and the male BBB here wouldn't know anything about a nest.