I think they are 'solitary' or mortar bees. I thought they were bumbles because some are huge. There hasn't been a swarm that I've witnessed. Internetz says wait it out till winter which is possible but we're having a ground floor extension soon and that'll be blooming awkward.
Are they honey bees?
http://www.bbka.org.uk/help/do_you_have_a_swarm.php
They can/will help if they are.