Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
Wet lichens are almost always more difficult to name; often they assume this green colour and other characters become hard to discern. It's not Parmelia, I feel sure.
Thanks Nigel - I'll see if I can find it again in the dry state, then re-photograph.
Found it, and it is dry.
Many thanks Nigel.
Lat/Lng: 51.309, -0.177
OS grid ref: TQ271582