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.
There are numerous lichens that form white crusts on rocks. Often, they are immature or barren and there may be little that can be done with them. (Often the case in urban areas.)
With luck they have some kind of reproductive structure, either sexual (usually apothecia) or asexual (isidia or soredia), but to see the latter we have to have a very close and pin-sharp photograph. Even then, chemical tests are often required.
Someone might be able to post a wild guess, but in my view your photograph is unidentifiable. Sorry.
If you happen to have a sharp close-up, then it might be a different matter.
Lat/Lng: 52.111305, -4.082479
OS grid ref: SN574479