Spiral (in part) mine in Nettle
No interactions present.
I agree it just might be anthacina but we cannot tell from the mine alone and one picture - though it does show some fine detail.
I am here because I am researching my own post today and will put a link here when it's up and running.
and here http://www.ukflymines.co.uk/Keys/URTICA.php
THREE MARINE PROJECTS
I have agreed but I may be the only one. I have completed my post and all the research needed for a positive ID. My find, first for the County, has been confirmed by a UK leading expert.
Lat/Lng: 56.0700713, -3.2433513
OS grid ref: NT226870