Probably 4th instar
No interactions present.
Thanks for all your comments on shield bugs- very interesting
I found these last week and was wondering if the black part on the thorax indicated a male or female?
There are a couple of shieldbugs with nymphs looking like this, but the pale margins to the dark pronotum on one of them means I think you're right with P. prasina. Should be Palomena, not alomena though
Have a look at the other observations at different stages.
Also this is quite a good identification sheet online.
Lat/Lng: 52.1, -3.4
OS grid ref: SO0451