There are two very similar brain fungi with yellow jelly-like and both are members of the family Tremellaceae. Most often here in West Wales we come across Tremella mesenterica, which is parasistic on crust fungi of the genus Peniophora. The other is Tremella aurantia, and it is not quite so common in our area; this jelly fungus is parasitic on Stereum hirsutum, the Hairy Curtain Crust. There is little to distinguish these two, and perhaps the best way to identify them is to take a close look at the substrate they are attached to; you should find that your brain fungus is growing from the remains of some kind of crust fungus, and you now know which is which (if you know your Peniophora from your Stereum, that is! Ain't fungi fun?).
Here is a picture of Stereum hirsutum:
And here is a Peniophora species:
Incidentally, the normally reddish-brown Leafy Brain (Tremella foliacea) has a pinkish-white form that could also cause confusion; however both Tremella mesenterica and Tremella aurantia are yellow or orange (or brown when totally dried up!) so if you do come across a whitish brain-like fungus it's neither of them.
Here's hoping you have/have had a very Happy Christmas!
Pat
