Silver grey foliose lichen
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.
Can't be 100% certain as Parmelia sulcata is very similar but has soredia rather than isidia on the lobes.
Lat/Lng: 50.6, -2.2
OS grid ref: SY9188