A small, dark bug associated with Ash. Males tend to be darker than females.  The rostrum is short, only reaching mid-coxae. Dissection of the male genitalia will confirm identification.

There are several similar Psallus species.  Psallus flavellus is also found on ash, but is smaller and a brighter orange/red in colour.

Check the length of the rostrum.  Provide photos of dorsal and ventral sides of a specimen, backed up by photo of male aedeagus, if possible; note the tree species from which it was collected. 

Ash trees

Common (ref: British Heteroptera checklist 2021 https://www.britishbugs.org.uk/systematic_het.html)

rarely recorded , but probably under-recorded