Lots of groups found on fallen Oak branches encrusted with lichens (Xanthoria parietina).

In Britain, N. aurantia (commonly known as Tremella aurantia) parasitizes Stereum hirsutum, which distinguishes it from Tremella mesenterica parasitises species of Peniophora.

As I understand it, both Peniophora and Stereum hirsutum can occur on any dead, broadleaf wood, so these could be either.