Diptera - Mycetophilidae

I've been busy shifting furniture, ripping up flooring, knocking out doorframes and chasing wiring at work today. My exploits into the world of coleoptera and diptera have been entirely restricted to a couple of minutes wandering around the laundry shed after dark whilst loading/unloading my washing. However, this particular outbuilding just happens to be situated in the middle of the hotel grounds and is lit throughout the night. In essence, it acts as a giant moth trap and I've encountered a great many spiders and insects in there the past couple of years. It can be surprisingly productive at times. 

The heavy rain that lasted all day today probably put paid to most flying insects, and the hordes of Amaurobius similis and Zygiella x-notata that live within the shed would have put paid to most insects already trapped in there from yesterday, but I did spy a single small fly on the wall. One quick pic with the camera and then it was safely popped into a tube.

Initially I thought Sylvicola, but it turned out otherwise

I started off with the RES Handbook to Mycetophilidae, gleefully figuring I'd have it to species in next to no time. Fool that I am. I keyed it through to subfamily Mycetophilinae which was followed by the sentence 'The Mycetophilinae are not included in this volume'. Bugger. At least I was fairly confident I had it to the correct subfamily, but where could I find a key?

Mike Hackston, my eternal hero, came to the rescue with his Keys to the British species of Mycetophilidae where it very quickly dropped out to Mycetophilinae using this key. Unfortunately, once again, there was no follow up key to this subfamily.

In desperation, I went hunting for something usable and came up with this very helpful key which dropped my fly out at genus level. Aha - now we're finally getting somewhere! According to this key my specimen is a Mycetophila. Ok, so how many of those are there on the British list, I wondered...

Three hundred and twenty three, according to record card RA64. Arse, that's quite a lot! 

As of this moment I still can't find a key to the genus Mycetophila, so that's as far as I can take it for now. Not an ideal start to the Diptera, but one that will be a recurring theme, I suspect. Here are some pics of the beast, body length approx. 5mm.

Note the small head, enormous hunchback and very long tibial spines

Tiny ocelli (arrowed) touching the compound eye - it's really very hard to see!

The microtrichia are arranged in clear lines - a diagnostic feature of subfamily Mycetophilinae

I had hoped to narrow it down to species level by combining the wing patterning with flight time and distribution, but that seems worse than futile considering there are 323 members of the genus with only about 4 readily found online. Mycetophila ornata seems to be the default species, but that's just not good enough. I need that key, it must exist somewhere!!!

As an aside, there's a Fungus Gnats Online site which seems quite amazingly informative, it can be viewed here. No key that I can see though.