A number of lichens growing in an area of of a few cm square, including Lecania sp (possibly erysibe), Lecanora sp, Caloplaca sp (possibly decipiens or flavescens)
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.
Links to photographs of Caloplaca decipiens:
and Caloplaca flavescens:
The rusty-red lichen might be Belonia nidarosiensis which is found on limestone and mortar but its not possible to be certain from the photograph.
Thanks again Jenny. Very helpful comments.
I need to take closer- up pix. The rusty red in this pic is ironstone I think (part of the wall - mixed blocks with limestone).
Always very difficult to do anything with immature crusts on stonework.
For what it's worth, looking at the photograph at maximum resolution, I cannot see anything I would guess would be a Lecania or Lecanora campestris, and I agree the rusty red is stonework and definitely not Belonia.
I'll not say that Lecania erysibe is NOT present, it would be too small to show clearly in the photograph.
My own guess is that some of the white crusts that are forming are Diploicia canescens. But they need to get bigger.
Lat/Lng: 51.9, -1.4
OS grid ref: SP4528