Found in leaf litter in deciduous woodland. Nightmare to photograph!!
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
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This does not look like the decurrent gills of M spirea but at only 2 mm it does not fit well with the other options(and at that size a great job of getting those photos).
M smithiana has a pink cap M capilaris and M polyadelpha (which I found a couple of days ago and didn't manage to get one good photo) are both paler than your find. I think without a microscope I would have gone for M hiemalis but I would not be confident enough to overrule you suggestion.
Mycena hiemalis isn't in any of my books but searching iSpot the observations do not seem to have the disproportionate stem length to cap size. I agree the gills do not look decurrent though.
Certificate in Contemporary Science (Open)
Lat/Lng: 51.418800368814, -0.95684051513672
OS grid ref: SU726693