This handsome fly, a male Graphomya maculata, was one of a number I noticed on late flowers on apple-mint Mentha x villosa in my garden at Nedd (NC137319) in October 2015. Since flies are not one of my areas of expertise, I collected a couple of specimens on 7th and had them confirmed by Stephen Moran (there is a closely related species); the photograph was taken on 14th.
It is a member of the same family, Muscidae, as the house fly Musca domestica (which I have never seen hereabouts), but rather more distinctive, with a stripy thorax and spotted abdomen in both sexes. The abdomen of the male is suffused with orangey-brown, as in this case.
The larvae are predatory, feeding in muddy pools and damp leaf litter (sounds like a description of my garden) and the adults appear late in the summer. Although widespread in England and Wales, there are only scattered records from Scotland, and apparently none from the far North-West.
Ian M. Evans