Sphagnum russowii
There are several publications and keys dedicated to the Sphagna of Britain and Europe. The most recent of these are listed on the Bryophyte identification page under Resources.
Sphagnum girgensohnii
Girgensohn’s Bog-moss
Sphagnum rubellum
Red Bog-moss
Sphagnum warnstorfii
Warnstorf’s Bog-moss