Phylum: Basidiomycota Family: Psathyrellaceae
Psathyrella cernua (Vahl) M.M. Moser
Usually found in fasciculate clusters as a saprobe on the wood of decaying broadleaved trees. There are few records and would seem to be genuinely rare
References:
Melzer (2018) Key to Psathyrella and related species
Overall (2017) Fungi: Mushroom & Toadstools of parks, gardens, heaths and woodlands