Liverwort/Moss/Lichen?

Liverwort/Moss/Lichen?

Observation - Liverwort/Moss/Lichen? - UK and Ireland. Description: I have no idea what this, which was growing on a tree is. Species ID would be great but any info including which group it belongs in would be useful (I've opted for plants.

I have no idea what this, which was growing on a tree is. Species ID would be great but any info including which group it belongs in would be useful (I've opted for "plants".