Phylum: Charophyta   Family: Gonatozygacea

Gonatozygon aculeatum  W.N. Hastings

Although described as widespread in circumneutral waters, it's rarely recorded which would suggest some scarcity

References: 
Brook, A.J. & Williamson, D.B. (2010) A Monograph on some British Desmids
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands
Ruzicka, J. (1977) Die Desmidiaceen Mitteleuropas, Volume 1, Part 1