A leaf spot fungus, possibly Guignardia philoprina, on a decaying holly leaf (Ilex aquifolium). Identification based on comparison with this image at the British Mycological Society's Fungi4Schools site. (The spelling G. phylloprena in that site [now corrected] appears to be an error, as it occurs only nowhere else out on the web and is not listed among the known synonyms of G. philoprina.)
The classification of the genus Guignardia seems to be in state of flux at the moment, following the realisation that its species are really just the sexual stages (teleomorphs) of species in the genus Phyllosticta (anamorphs). See here, and half-way down this page, for more details. Getting the classification of these fungi right is important because some of them are economically significant plant pathogens.
Photo taken in the Wilderness, Whiteknights Park, Reading University grounds, Reading, UK, on 2010-02-13.
It could also be Trochila ilicana, which also appears in the excellent Collins Complete Guide to British Mushrooms and Toadstools (Sterry and Hughes, 2009). However, on this page at Janusz Blaskowski's Saprophytic, Pathogenic and Symbiotic Fungi of Poland site, the spots on the leaves look quite different.