Fungus fruiting on underside of compostable plant pot (Chili pepper plant growing inside).
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
Hence my lack of confidence in the identification. It is usually found on wood, I think.
What was the texture? If it would squash easily and release a coloured "paste" then it is a slime mould. If it doesn't squash it is likely to be a Ascomycete. I think the latter is more likely.
The shape is also wrong for Lycogala. You can see many of them are disc shaped. Not a slime mouldm as Flaxton says, more likely to be an Ascomycete.
Lat/Lng: 53.3245, -3.4753333333333
OS grid ref: SJ018818