Finally managed to visit Eype beach at low tide and was very happy with the result. Completely legitimately within the square there is a good area of seaweed encrusted boulders and even some rockpools. Only there for half an hour (it was decidedly cold and with a bitter wind) but in that time photographed 12 species of seaweed. Not all ID'ed yet but gives me hope.
Also some Honeycomb worms tubes (Sabellaria alveolata), I think? Photo below.