Small, but Perfectly Formed

As there are approximately 250 solitary bee species in the UK, I'm not sure about this tiny one, measuring only 6mm in length. It could be one of the Mining Bee group. Any experts out there?

My red sedum 's flowers opened in earnest today, followed soon after by dozens of these tiny bees, descending in a feeding frenzy. It's a challenge to get a clear photo, as in addition to their tiny size, these little guys don't stay still for many seconds.