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.
Nice photo, showing the context well, but there are several grey lichens that can form extensive crusts on gravestones, and I am afraid that without a high resolution, close up view, any ID would be pure speculation. Chemical testing is often necessary, which iSpot has not yet made possible on the posted photographs.
Lat/Lng: 51.7, -4.4
OS grid ref: SN3610