Found on ground ivy (Glechoma hederacea)flower at the grassland/scrub edge border.
No interactions present.
Thanks Dave - I look forward to the new key!
Is the foodplant Dog's Mercury? If so, there was some adjacent to the Ground Ivy.
I've added a couple of pics that may help determination...
Lat/Lng: 51.3007, -0.1789
OS grid ref: TQ270573