Curious Behaviour - Bee

Last Spring we invested in an insect house - the label declared that it was for lacewing and ladybirds to hibernate during the Winter. The directions were quite explicit - fix so that the box faces a southerly direction. The ideal spot was found and it was securely nailed to a small garden shed. The Summer arrived and slowly the wood faded, by Winter it looked as though it had been there for a good five years. There were no signs, however, of any ladybirds or lacewings - just the odd woodlouse. Yesterday though the strangest thing occurred. I noticed that a few of the bamboo lacewing shelters had been sealed over. Shortly afterwards, a couple of bees came buzzing around entering the holes then turning around and coming out again. This was happening all day. I'm not sure what variety of bee they are, although they do resemble honey bees. What are they doing? Are they making this into a hive? Could they be breeding in the insect box? I suppose we shall have to wait and see!!