Sorry to ask in here but the bees that are solitary and live in holes in the ground are they bumble bees rather than honey bees ( and are there larvae big orangey/yellow things sure I dug one up a couple of years ago ? Seen one today 'looking' in the slabs for a suitable hole for a nest (at least that is what I assume it was doing).
To add SOME relevance to this group, 'slab' it was looking in had been a side of a coal bunker that was doing service as a paving slab, bunker had been dismantled as it was an eyesore and the various parts were skipped or used as paving slabs, was quite amusing watching me trying to break up the pieces of bunker with an 8lb mash and a reciprocating saw to deal with the rebar.