Pair of tiny flies. Some form of midge perhaps? (View full size to see the wonderful antennae on the male.)
No interactions present.
I love the photo and I agree that the male's antennae are wonderful!
I've had a look on Diptera.info and am now fairly sure these are Ceratopogonidae.
Thanks John, although I don't have a marsh in the garden they were next to the plant-clogged (and fishless) garden pond which I presume would be suitable habitat.
Lat/Lng: 52.6, -1.2
OS grid ref: SK5501