Dark, flattish, shapped like cushion buttons with tiny warts.
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
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You're probably thinking of the yellow Tremella mesenterica, which some people also refer to as witches' butter, but this looks good for Exidia glandulosa.
I hadn't realised that until now. I see Wikipedia lists T. mesenterica common names as including the yellow brain, the golden jelly fungus, the yellow trembler, and witches' butter. Whereas E. glandulosa is known as black witches' butter, black jelly roll, or warty jelly fungus! I agree that this is the latter.
Did my ID from a Collins guide as its not something I am familiar with. It shows both yellow and black versions.
Lat/Lng: 53.5633, -2.1748
OS grid ref: SD885074