Found on dead wood, reasonably dry.
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.
It isn't Lecanora campestris though I can't be sure from the photograph what it is.
Links below to photographs and details of L. campestris for comparison:
At least 3 different crusts here, but none of them L. campestris. One is probably Lecanora chlarotera, but microscopy and chemical tests needed. Also probably Lecidella elaeochroma and Arthonia radiata.
L. campestris is a species of rocks and walls, appearing on trees only when there is a lot of mineral dust caught up in the bark.
Lat/Lng: 52.838, -1.555
OS grid ref: SK300268