Bad phone photo, I'm sorry. About 1 cm long, brightly coloured with spectacular iridescent spots down the side of the wing covers. I'm guessing a leaf beetle, and maybe Calomela genus.
Thanks Jackie. Yes, I put it in as un-ID leaf beetle as that was as close an ID as I could be fairly sure of. I didn't select Calomela as that was a real guess.
Oh dear, I think I need a better photo! Thanks very much, Max. Both species seem variable in the photos on those sites too, which makes it harder. My impression of it was as a generally lighter green overall than many of the juncta images. I'll just have to find another one!