Bumble bees in house

[Juliet1200]

I've had two red tailed bumble bees in the house in the last couple of days. The first one was there when we came home after being away overnight. It was stuck in the sink, not sure how long it had been there but it couldn't fly. Soon clambered up on to the forget-me-nots when I put it outside in the sunshine and was flying before long The second one was there when I came home from work today.

The windows had been shut both times. There are vents in the window units, but I think it's unlikely they'd be coming in through them.

I also had to move the insulation from around the outside tap yesterday so one could escape from the small hole behind it, and I have previously seen them investigating the air gaps between the bricks outside.

Am I right in assuming they've been hibernating in the walls? I know there is a way in from outside as the mouse comes and goes at will

If they've been hibernating, will they stay out once they're out, or are they likely to be nesting in there?

I'm planning to block the gaps outside (with a little metal grille thing) in an attempt to keep the mice out, but I don't want to trap the bees inside!

Any advice would be very welcome