I'm not quite sure what to think about this. On the one hand, bees are awesome, and having planted a variety of bee attracting plants, it feels a bit churlish to complain that some have turned up to take us up on the offer. And unlike some kamikaze wasps I could name, these bees seem to be quite happy to bimble about, minding their own business.
On the other hand, part of me worries that they'll slowly spread throughout the entire cavity and turn the house into a massive hive. Or, more plausibly, cause problems by bringing stuff into the cavity which the cavity was not supposed to hold, causing untold cost to repair and replace.
So what should we do?
Nuke the bees from orbit - it's the only way to be sure.
Try and persuade the bees that houses are for people and not for insects, fuzzy and awesome though they may be.
Commend the bees on their industrious production of hexagonal cell insulation, and leave them to get on with it.
Stick a webcam into the hive to observe what is going on, and evaluate the feasibility of installing a honey-tap.
Bow down to our new buzzing overlords.