Can anyone help by identifying this bee? We've just moved into a new house & there are a lot of these bees at the back of the house. They're flying round the wall & look as though they might be crawling into the little plastic spacers set inbetween some of the bricks. It's a south-faceing wall so are they attracted to the heat? Are they actually bees & is it likely they could be nesting in a newly built (2months old!) wall? Any help would be much appreciated!