Troop growing on oak.
Cap up to 17mm.
Smell strongly of ammonia.
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.
Is Mycena alcalina. The comment is a bit cryptic: "Much of the British material under this name has been found to be Mycena stipata".
Mycena alcalina was my ID from Philips but then as I did a little more research I found the same comment so changed to stipata.
Lat/Lng: 53.698, -1.9279
OS grid ref: SE048223