Christina Websell wrote:

I am very interested in Sacha's comment, about having a 'hive' for
bumble bees. Have you heard anything about those?

Yes. They are easy to make, have a look on the web. I've made
several and they've all been taken up.
I've also drilled a log with holes for solitary bees and some of
holes are blocked up with clay, so I guess a few solitary bees found
it a good place to lay their eggs.

How do you attract them, or do they just find it?