I read your story today (it was unavailable yesterday) you really seem to have your bees sorted
I have tried bamboo tubes around 3"dia filled with sheeps wool (yes off the barbed wire)
and a hanging basket mix of wool and horsehair/moss(asda).The tubes have the ends plugged and a long entrance fitted and are placed anywhere bumble bees search in the garden ,secured with zip-ties(cable ties)to fences or shrubs
Alas still no takers but at least I am giving them a chance (bee-napping bee-ing considered)