A rust fungus commonly found on Coltsfoot (Tussilago farfara).
Edit: Changed to match AlanS's ID. Many thanks.
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.
Yes, well documented here http://www.bladmineerders.nl/gallen/fungi/coleosporium/tussilaginis/tuss... but easy to assume a puccinia.
Lat/Lng: 55.4737, -3.2026
OS grid ref: NT240206