STEREUM HIRSUTUM FUNGUS
Usually referred to by its botanical namel, but also called Hairy Curtain Crust or false turkey tail.
The firm identification here needs to be taken with caution (Check with an expert). As the FirstNature website says, No matter how many of these attractve bracket fungi you see, there will always be another Stereum hirsutum with significantly different coloration. The variability of this fungus makes its identification at first rather difficult.
Stereum hirsutum is common and widespread throughout Britain and Ireland. On mainland Europe this crust fungus is found from Scandinavia right down to the Mediterranean region.
That website goes on to say : Stereum, the generic name, means tough, and crust fungi in this genus certainly can be difficult to tear when you want to take a small sample for investigation. The specific epithet hirsutum means hairy (hirsute, indeed!), and the upper surfaces of these irregularly-shaped tiered brackets are distinctly hairy when the fruitbodies are young and fresh; however, they do become smoother with age.
The common name Hairy Curtain Crust reflects (in the 'curtain' part) the rippled form of edges of the fruitbodies, which do look like partly-drawn curtains; however, it's very much more common to see this species growing in the form of tiers of reflexed crusts or brackets, particularly on standing dead wood, than as resupinate crusts (although the latter form does occur, and I see this most often on the ends and vertical faces of stacked sawn timber).
This example was found in Craig Andro Woods below the Hundred Steps on the way to Carman Muir.
FIRST NATURE website : https://www.first-nature.com/fungi/stereum-hirsutum.php#:~:text=Stereum%20hirsutum%20is%20common%20and%20widespread,one%20of%20those%20truly%20international%20fungi%2C&text=Stereum%20hirsutum%20is%20common,those%20truly%20international%20fungi%2C&text=is%20common%20and%20widespread,one%20of%20those%20truly
WIKIPEDIA : https://en.wikipedia.org/wiki/Stereum_hirsutum#:~:text=Stereum%20hirsutum%2C%20also%20called%20false%20turkey%20tail%20and,other%20species%20such%20as%20the%20fungus%20Tremella%20aurantia.