Pretty sure this is a Lecanora sp. but not totally sure which one, possibly L. muralis? Hope someone can help out, thanks. Found growing on a concrete boulder.
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.
L. muralis, as you suggest. It is described as sometimes being pruinose, but I haven't seen it looking like this. A coastal thing, perhaps?
There are 3 other placodioid Lecanora spp. known in Britain, but none of them tally, so I'd agree with L. muralis.
Lat/Lng: 54.2086, -0.2845
OS grid ref: TA119805