Growing on the ground on a sandstone paving slab.
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 is difficult to make out any critical detail here. As always, crustose lichens require pin-sharp photography, as the identification features often require a hand lens.
There are a few visible apothecia that might well be of a Lecanora, but also black things that I think are apothecia, though the possibility of immersed perithecia also occurred to me. There might be more than one lichen present.
Of course, when lichens are on paving stones, people walk on them, so it is often not easy to put names to these things that look like trodden chewing gum.
Lat/Lng: 51.4739, -2.5857
OS grid ref: ST594751