Three species of Bibio flying today...this one the commonest.
No interactions present.
..agreed not through experience but because I used your detail to look this up.
Thanks for your interest in what is an interesting family of flies. They take a bit of getting used to, not least because the key by Freeman and Lane is a bit out of date and some species have changed. But, supplement that with Steven Falk's excellent photos and they are not too bad, after you've seen a fair few (under a microscope, too)...
My Flickr photos...
Lat/Lng: 53.938181453516, -0.85672974586487
OS grid ref: SE751497