Photographed on the rocky shore at Maenporth during the BioBlitz 2008 undertaken by students.
No interactions present.
I have agreed!
You've been very patient Jason.
This is probably the Green-leaf Worm (Eulalia viridis) not a thread worm.
Much more is on the web about this now - see
See my recent post here
It is about the eggs but has started a good discussion.
Lat/Lng: 50.1, -5.1
OS grid ref: SW7929