See Dr Google’s description below. We are seeing many such holes and bees around The Gables this year
In the UK, miner bees, also known as mining bees, are a group of solitary bees that nest in the ground, digging tunnels and chambers for their young. There are over 224 species of solitary bees in the UK, with many belonging to the mining bee group (Andrena genus). They are important pollinators and are generally harmless, with their stings not being strong enough to penetrate human skin.
gfreedmanblog 
I also have these holes – must go out and watch them to see if mine are also made by mining bees. Thank you for investigating.
Sent from my iPad
They are fascinating