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Well-spotted Theo, I was lazy and just going on the "look and feel" of the fly with it's slightly yellow-brown dusting on the abdomen, which is common in bombylans and currently we seem to get more bombylans reported than any other Carcelia species.

With a dark basicosta it has to be one of: tibialis, lucorum, gnava or atricosta but the latter 2 are incredibly rare here. Working on Belshaw's key (which we are currently updating with a few more species - work in progress) I think I can see discal bristles on tergite 4 and 1 antero-dorsal bristle on the mid tibia, which would suggest it is tibialis. It's still a bit hit & miss without the specimen to examine closely, but it's as close as you'll probably get I think B)

With a specimen it would be more straightforward and if it was a male we'd be able to use the very good features of the male genitalia. I'd say Carcelia are not really as bad as Siphona to identify, and there are worse genera (like Thelaira, which is currently under revision) ... but they're certainly not easy from a photo :)