Looked a bit like flies, very tiny, all facing in the same direction on a fence post.
No interactions present.
I think that it is a swarm of flying ants.
University of Edinburgh and Biodiversity Observatory (OU)
I agree they're flying ants. But the picture isn't that clear.
Definitely flies. Look at the largest resolution and they are clearly not ants. I'd go for some sort of blackfly, but I don't know which ones fly so late in the season.
These are flies, and look similar to ones we've discussed previously on iSpot:
In that discussion we weren't sure whether they were flies in family Bibionidae or Scatopsidae, and I think these are the two likely candidates this time round as well. My guess would be for family Scatopsidae, following ChrisR's advice from the previous discussion, but I don't know that family well enough to confirm it.
It would be worth you editing this observation to put it in the Invertebrates group (rather than "Other organisms") as more people are likely to see it there.
Entomologist and biological recorder
Observation moved from other organisms' section to one of the other areas where it fits in better and people interested in this group of organisms can find it more easily. Other organisms group is only for things that do not fit in any of the other sections, for example bacteria, viruses, slime moulds or things that you have no idea which group to put them in.
Lat/Lng: 52.2, -2.2
OS grid ref: SO8858