Sadly I have not been able to find out much about the grey-patched mining bee (Andrena nitidi) and the best source of information can be found on the Bees, wasps and ant recording society's web site here: http://www.bwars.com/index.php?q=bee/andrenidae/andrena-nitida. For those of you not wishing to follow the link here is a summary of some of what is known about this species.
This is a large species of mining bee (one that excavates a nest under ground). It has a reddish (foxy) brown thorax and a shiny (polished) abdomen but the female has grey hairs on the thorax which is where the common names comes from of course. It is a fairly common species in southern Britain, less so further north, and is generally active between April and June on grasslands. It feeds on the pollen of several types of flower including dandelions,
This species is believed to be parasitised by other species of bee, particularly Gooden's nomad bee.