I was quite excited about this fly when I got it from willow catkins yesterday, but I quickly ran into bother and never got out of it again. Hopefully someone from Dipterists Forum can help me get untangled.
Update: thanks to DF I can now say this is one of the Empididae. So that's a step forward.
Empid key (link):
1. Discal cell present -> 3
3. r4+5 not forked ->4
4. "Lower branch of vein cu longer and joining anal vein
at an angle much greater than 90°. Proboscis long
or very long, directed downwards."
-> Genus Rhamphomyia
Let's park this one there for the moment ... at least until I find a key. Lots of species in the genus, but NBN (usual caveats apply) has only one record for Fife, from the usual place.
There is online an amazing resource, which goes far broader than only this one, but the keys to the Empididae are here: link
Rhamphomyia keying ...
1. Axillary lobe of wing well developed, the axillary angle rarely more than 90 degrees. 3rd antennal segment not particularly long and slender -> 2
2. Vein bordering upper side of discal cell always distinct, although sometimes noticeably less pigmented than other veins. Discal cell usually short and truncate at tip, rarely elongate and then the upper outer corner very little produced or the discal cell is open -> 5
5. Thorax black or grey -> 7
7. Acrostichals always present. Legs dark (except in barbata and sometimes geniculata). Stout or plump
species, male never with thorax velvety black and often with large and conspicuous genitalia -> 15
15. Labellae of proboscis long and slender, very short-haired, the hairs not so long as labellae are wide. Labrum at least one and a half times longer than head is deep. No bristle in 'comb' at tip of hind tibiae behind. Small species around 3 mm. Subgenus Aclonempis.
Ohhh, close but no cigar. 3mm?! Nope. Rewind and back to the microscope