Dicranum scottianum is a hyperoceanic moss, so it is confined to high rainfall districts and situations where there is constant high humidity and an equable temperature range. So, except for a few sites in the Weald, it is mainly confined to the western seaboard of Britain and Ireland.
The species it is most likely to be confused with, especially in the absence of mature capsules, is D. fuscescens. Habitat can provide some clues though, as D. fuscescens is far more tolerant of cold and exposed situations than D. scottianum.
Vegetatively, D. scottianum lacks papillae/mamillae on the upper leaf lamina and has a smooth to slightly toothed leaf tip, so these characters will help to separate it from D. fuscescens if there is any doubt.Read the Field Guide account