Parmelia, but difficult to distinguish between sulcata and saxatalis
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.
Quote: "White sorediate spots rather than cracks/networks, browning near centre"
That part of the notes you've added to your identification could be a bit misleading.
Parmelia sulcata: The white reticulation can often form a +/- continuous network of lines on the thallus and the lobe ends are often brownish.
Punctelia species have distinctive raised white sorediate spots (pseudocyphellae) on the lobes.
Lat/Lng: 54.5, -6.0
OS grid ref: NW4424