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Oh nice, yes.

The chaetotaxy didn't look quite right for the similar Spilogona
And none had the projecting chin in quite the same way
Which seems distinctive

Of the three Thricops on the list
Thricops cunctans does not have the protruding chin
Thricops longipes has thoracic marking

In Steven Falk´s Flickr account for UK Muscidae he notes the other two Thricops with black legs and protruding chin in UK have a complete row of anteroventrals on hind femora. So this is concurrent with T.rostratus in regard to UK fauna too, with only 3-4 AVs.
https://www.flick...297408293/

At a similar latitude in Norway there are two with distribution visible on ArtsDataBanken not present in UK list so not covered by Falk.
T.lividiventris and T.furcatus.
T.lividiventris doesn´t have the projecting chin.
I am unable to find an image of T.furcatus yet.

But T.rostratus is so common here in Iceland that it even warrants a common name - Trjónufluga
https://www.ni.is...-rostratus

So overall, seems very plausible.
Thanks John