No interactions present.
This one has reproductive structures at the end of the fronds (top left of photo) that are flat, orangy and bumpy. In F. spiralis these are swollen with a distinctive rim round the edge. 'Spiral' is not a feature that is always reliable; another common name for F. spiralis is 'flat wrack'.
I was a bit confused since it looked so different from the other serratus I saw further down the shore
Lat/Lng: 50.2785, -3.9013
OS grid ref: SX646437