Cnodacophora sellata (Meigen, 1826)

Identification: Thorax: Much of the thorax dusted so as to appear grey, except humeri which are black & undusted, Head: Long palpi
Antennae: Pedicel (2nd antennal segment) dark, blackish brown. Wing: infuscated (rarely evident in photographs)
Males: A metathoracic process ("rudder")  projecting between the hind coxae (arrowed in Image 2)
Size: Larger species than C. stylifera. Wing length 5.5 - 7.4 mm

Distribution

Europe: Countries (2018 ) (Sumner, 2018), online at Fauna Europaea, Occurrences at GBIF
UK: Recording Scheme map of occurrences 2016 (verified.) Online (NBN Atlas) via Easy maps or Interactive Atlas