These are Red Mason bees, Osmia rufa. Although a solitary species they nest in aggregations and often use a common entrance to a cavity, though each female will construct (from mud) and provision her own brood cells.
Great video - I could watch it all day. I get heaps of enjoyment watching hundreds of these and their smaller cousins the Blue mason bee visiting my very large solitary bee house in the garden. all helps to keep the plants in the garden pollinated.