White crustose lichen growing on a stone church in Poole town centre.
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.
Unfortunately the photo doesn't show enough detail for identification - could you post a larger close up showing fruiting bodies etc?
However its definitely not Pertusaria hymenea as that species is found on trees and not on rock or stone:
Lat/Lng: 50.7167, -1.9831
OS grid ref: SZ012907