Taken last year around 20th May South Coast UK. Not certain of the size but between 1 to 2 cms. Seemed to be black all over including the wings with no visible markings- 2 pairs of wings?
Ah thanks- this makes sense now- Think it is Phymatocera aterrima -Solomons seal sawfly- I get this every year (the caterpillars) and this was taken near the plant