Lots of kelp washed up on shore after heavy winds. Most was Laminaria hyperborea, but there were just a few specimens of Saccorhiza polyschides.
No interactions present.
There is a good picture on page 159 of one of Francis Bunker's kids holding a whole plant that shows well the structure you photographed. I don't know anything else in UK waters that looks like this. There are numerous records from the Northumberland coast in the Cullercoats Flora and Fauna, mostly of drift algae.
Lat/Lng: 55.6126, -1.7106
OS grid ref: NU183354