Thanks once more to my bee-friend I now know what these bees are… its a bit shameful really as a closer inspection of the picture would have made two things obvious… Firstly, they fact they are collecting pollen on their legs rules our the Megachile species I was plumping for because they have pollen brushes on the underside of their abdomens. And secondly, a better look at the legs would have given me the common name!
Yellow-legged Mining Bee Andrena flavipes
The yellow legs are clearly visible in the picture above
Below is another Andrena species – mining bee. However, my friend couldn’t give an ID, perhaps crucial diagnostic features are not visible. [Note to self, take pictures from as many angles as possible to get all of the bee in view]