The venation and mouthparts can be seen, is it a female?
No interactions present.
This is one of the many species of fly that go under the general name 'green-bottle'. I think Neomyia cornicina is the most likely option, and I agree it is a female (due the the broad 'frons', or face area between the eyes).
A diagram showing where the 'acrostichal bristles' are is at:
Entomologist and biological recorder
Thanks for your comments, I've got no idea about insects at all
Lat/Lng: 52.1, -3.4
OS grid ref: SO0451