I think they might be the Buff-Tailed bumblebee, or Bombus Terrestris, happily they're fairly common, and are not among the endangered species of bumblebee. There seem to be a lot of them. They were coming and going every few seconds as I was stood there.
I like having bees living in the garden. It's reminded me of my ambition to keep a hive or two, and to have my own fresh honey for breakfast and my own home-brewed mead at suppertime. I would also like a goat, some chickens, and an orchard. And ducks.
I had intended to take better pictures than these for the blog, but I got nervous with the loud, buzzing, furry things which were barrelling past my ear. I know they're docile and are seriously unlikely to sting, but when you're right up close to the nest entrance, and the bees are getting nervous and beginning to show signs of dive-bombing, you don't tend to stick around too long for the perfect macro shot.
(These were taken from the other side of the shed, using zoom.)