No identification made yet.
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I think it may be a ragworm of some sort? Though looks very large in comparison to the barnacles.
I also thought it might be a ragworm but am not sure.(if I squint at the pic it sort of looks like a tiny sea cucumber too).
Possibly a nudibranch upside down...
Lat/Lng: 50.156, -5.0711
OS grid ref: SW807329