Firstly, this likely not a swarm of honey bees. Honey bees do swarm in late spring and th emiddle of summer, but they are following, very closely, the queen bee. When they stop, they swarm on a branch or other surface in a great group all trying to be as close the queen as possible.
My, guess is that you have an infestation of wasps that are often, at least here in the U.S., mistaken for bees.
If it doesn't appear that there are a large number of the critters, the best course of action would be to have a good handyman seal up the entrance to where they are going. The few that are on the inside will die quickly. There shouldn't be enough to cause any smell. The entrance can probably be sealed quickly with a good caulking gun and approriate caulk (which is what should have been done by whoever drilled the area anyway).
Good luck!