Phylum: Ochrophyta   Family: Acinetosporaceae

Pylaiella littoralis (Linnaeus) Kjellman, 1872

A brown thallus but fading to yellow. The fine filaments are richly branched, usually opposite, and can be twisted like rope near the base. Found intertidally to offshore, often epiphytic, particularly on fucoids, and free floating

References: 
Newton (1931) - A Handbook of the British Seaweeds