This cup fungus has sprung up all along the length of the bed:
the same colour as the outer surface, but forms a separate layer with a slightly smoother texture.
It doesn't have much of a stem to speak of.
Having consulted with the Collins Complete (photographic) Guide and the Collins (illustrated) Fungi Guide, I'm going to take a punt on this being Blistered Cup Peziza vesiculosa:
For the record"Distinguished by its clustered, blister-like growth. Fruits year-round. FRUIT BODY To 8cm across; initially deep cup- or goldfish bowl-shaped with a strongly inrolled margin, but expanding to saucer-shaped with the margin splitting and becoming ragged or blistered; inner surface yellowish brown with a smooth texture; outer surface similar in colour and finely granular. HABITAT Typically in tight, fused clusters on straw, manure, compost and rich soil, and increasingly on woodchip mulch. STATUS Widespread and common."
Location: Small Dole
Grid reference: TQ2112
Entered into FRDBI: 13/02/2017