Finally found the Small Copper- on a flowery stretch of field margin near Oughtonhead Common in Hertfordshire. As is often the case I have Jif to thank for his directions to more or less the exact spot where they are most active.

 Proved to be a good locale for a variety of butterflies including Brown Argus. I published photos of an Argus basking a couple of days ago; the underwing (as seen below) is very different to the upperwing.