Iain MacGowan has recently (June 2015) found Okeniella caudata (Zett.) at two localities in high level flushes above 850m in Perthshitre and Angus. It looks a bit like Pogonota barbata in that it has a fan of long golden hair on the genitalia, but lacks the "beard" of simlar hairs on the jowls and also does not have the modified male wing veination of that species.
Members of the genus Okeniella are distinctive in the male because, apart from the upward pointing fan of long golden hairs on the hypopigium, the 5th abdominal sternite has very distinctively shaped processes. Three species are known, of which two occur in northern Europe - O. caudata and O. dasyprocta. According to the country level distribution maps given by Fauna Europaea, they have similar distributions - occuring in Norway, Swededn, Finland, Latvia and Russia. They are fairly easy to tell apart - the wing of O. caudata has long hairs on the underside of the Costa between Sc and R; and the processes on the male 5th sternite are of different shape: in O. caudata they are "L" shaped, whilst in O. dasyprocta they are "T" shaped (illustrated in Godrokov's key to the Insects of European Russia). Iain's photographs of his specimens (below) show both the hairs on the wing and male abdominal characters of O. caudata very clearly. I have not nbeen able to discover anything further about the biology of O. caudata, via Google searches, but it is Holarctic and recorded from North America.
Iain expects to publish this addition to the British list in a forthcoming volume of Dipterists Digest.