On acid rocks at Bradgate Park, Charnwood, Leics.
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.
The green patch looks like it is a parasitic fungus. A few such things are known on Rhizocarpon geographicum now, but I don't have a suggestion for this one.
Thanks Alan, I was hoping that was a possibility. It's the first I've seen, but I see from your site that they are not uncommon.
Lat/Lng: 52.6, -1.3
OS grid ref: SK5310