Unknown bees

Unknown bees

Observation - Unknown bees - UK and Ireland. Description: These bees had made their nest in a pile of grass cuttings that had been left next to a pair of ladders so they were reasonably well hidden from predators. What surprised me was the nest was open rather than fully enclosed. Could anyone identify what sort

These bees had made their nest in a pile of grass cuttings that had been left next to a pair of ladders so they were reasonably well hidden from predators. What surprised me was the nest was open rather than fully enclosed. Could anyone identify what sort of bees they are?