The largest part of the autumn fungus fruiting season may have passed in the UK, or at least where I live, but there are still a few things around, if you're prepared to look closely for them.
Yes, it's a fly (I don't know which species), but it is a fly with a fungal parasite, Entomophthora muscae. The fungus grows inside the fly, eventually reaching the fly's brain and influencing its behaviour. The fungus needs to get as high as possible to ensure reproductive success, so it forces the fly to climb to the top of a flower, twig or, as in this case, blade of grass and then makes it hold tight. In some cases I've even seen fungal hyphae around the flies proboscis and legs where the fungus has apparently anchored its host (though I suppose this could be a secondary infection in older specimens). The fungus then kills the fly and bursts through its abdomen to shed its spores. These spores are picked up by the wind to infect the next generation of flies.
E. muscae isn't rare by any means, but it does seem to be overlooked. It also seems to be most abundant as it starts to get wetter in autumn, so I find it most years at about this time. Nevertheless, I have very rarely found as perfect a specimen as this.
I know there won't be many others who share this opinion, but I do think that E. muscae is rather awesome.