Aphthona nonstriata
I'm not quite sure if the leaf I found this on (in the photo below) was Yellow Iris (which it's typically found on) or Common Reed, but both were in the immediate vicinty.
female Aphthona nonstriata showing pronotum and spermatheca, Wendling Beck Environment Project (Norfolk, UK), 26th May 2023
This one was defintely on Yellow Flag Iris, at a different site within the same project area.
female Aphthona nonstriata showing frons, elytral humeri, pronotum, hind tarsal claw and spermatheca, Wendling Beck Environment Project (Norfolk, UK), 14th May 2022