Puzzling bees

I found lots of tiny burrow openings in small piles of fine chalky soil in one of the ex-arable fields at the nature reserve. After watching for a while a spotted a couple of these mining bees excavating new burrows. The thorax is covered by yellow-brown hairs as are the legs, which are also loaded with pollen, giving them a very striking bright yellow look. The problem is that the species I thing it must be, Dasypoda hirtipes or Hairy Legged Mining Bee, is (a) not supposed to be flying until late June and (b) has not been recorded within about 20 miles of the reserve. More investigation needed!