Is this a typical Herring Gull?
No interactions present.
Personally, I would not worry about the subspecies unless it was clearly one or the other. Many argenteus approach Scandinavian argentatus in size and colour, but some argentatus are noticeably larger and darker on the mantle and easily assignable to that subspecies. With no other bird to compare this one to, it all becomes a bit subjective. I suspect you are right with argenteus, but I don't think you would easily prove it.
My Flickr photos...
Gull ID is a bit of a minefield isn't it. I was surprised to see rather little dark streaking on the head and nape for an October bird, and an odd leg colour (not in the photos) got me a bit excited initially, but it doesn't really seem to fit anything else either!
Some larophiles devote hour upon hour to them and become obsessed. I gave it a go for a while, but life is too short! The following site is useful for comparison...
I suspect this is a third winter bird, on the bill colour. In flight it might show some brown on the wings, or it might not.
Many thanks Bob - very interesting!
Lat/Lng: 51.1925, 0.2506
OS grid ref: TQ573461