I am pretty sure this is a bryozoan but unsure. It appears to have colonised a piece of seaweed. It could be sea chervil or hornwrack maybe??
No interactions present.
I'm sure not Alcyonidium diaphanum,as the 'other observations',show (smooth & no cell structure). Looks a bit like hornwrack but the cells seem so large & such long 'hairs'!
Alycyonidium diaphanum grows on stones and boulders,and is not listed as growing on seaweeds. Hornwrack, Flustra foliacea, is listed as growing on stones and shells, not seaweeds.
Ref: Hayward.P & Ryland,J. 2003 Marine Fauna of North West Europe.
Seems JoC has it; which'd mean very small 'cells' as marlin says zooids .5 or .7mm long
Lat/Lng: 54.4904, -3.6152
OS grid ref: NX954117