In their hundreds, if not thousands. Definitely dimorphic.
No identification made yet.
No interactions present.
Mick, you've got LOADS of these languishing in the Help with Confirming.. carousel.
I can't help with ID's (who can?) but it is an interesting area and I WOULD like to help with some additional research.
Are these widespread in the UK and are there a huge number of lookalikes?
That you are quite experienced with these things and, I suspect, have exhausted all the resource available, means a dead end for me.
It's nice to see several pictures from different angles.
Two things, though, I'd like to say; one is that scale in pictures would be quite useful and some ID or Descriptive notes would make it easier for anyone trying to help - I am.
THREE MARINE PROJECTS
Lat/Lng: 53.2085, -0.5595
OS grid ref: SK963689
Stagnant puddles on land side of concrete bank.