Can anyone shed light on the identity of this insect from a UK garden?

With scant bristly hair, over large eyes that take up most of the head and an untidy collection of pollen, this is the kind of bee only a Mother could love. Not beeing an authority on bee species, it’s difficult to classify this particular one. Is at a Mason bee? A leafcutter bee? Or maybee it isn’t a bee at all but a kind of hoverfly or other mimic.