small fronded plant-like marine organism bedded in sponge
No interactions present.
I think this is a hydroid of some kind - looks superficially like Nemertesia (see http://www.marevita.org/donnees/Cnidaria/Hydrozoa/Hydroida/Leptomedusae/...). I'll try to refer this to someone who knows more than me...
Lat/Lng: 52.9, 0.6
OS grid ref: TF7745