No interactions present.
We could also consider Palmaria palmata. In the Marlin link (above) the Additional Information on C. ciliata says "Calliblepharis ciliata is very similar to Palmaria palmata. However, the latter (P. palmata) has a disc shaped holdfast."
This photo does not show a holdfast, which is the easiest way to distinguish on the shore. There are some bryozoans growing on the frond, but these need a microscope for ID.
I did consider this species, but the general appearance suggested C. ciliata to me because of the shape of the branchlets and because there appear to be branchlets coming out of the main blade. I'm no seaweed expert though, so I may well be wrong...
Regarding the bryozoans, are you saying that there are specific bryozoans for each of the seaweed species, which would help to make a positive ID, or is that just a general comment?
I agree, it could be either red seaweed; without the holdfast we cannot be sure from the photo.
There are some bryozoans that are specific to one or a few seaweeds, but many others are more catholic in their habitat preferences. For example, Alcyonidium gelatinosum is found on Fucus serratus, very rarely on other algae. Membranipora membranacea is common on Laminaria fronds, rarely on Fucus serratus. Electra pilosa is common on a wide range of lower shore algae. Looking at Animals on seaweed is a wonderful way to spend time, especially with the excellent book of the same name by Peter Hayward, published by Richmond Publishing.
It's interesting to know a bit more about bryozoans.
Lat/Lng: 50.71892, -1.85132
OS grid ref: SZ105910