> According to Google Maps, "Hopwood is a suburb of Heywood, a town within the Metropolitan Borough of Rochdale, in Greater Manchester, England", so that fits too. Thank you very much, Richard. <

And thank you too. I had tried Multimap, which hadn't found it. Google Maps not only finds Hopwood but shows Hopwood Hall College and Hopwood Clough Nature Reserve close to the railway line about a mile south of Castleton. So it seems very plausible that there would have been a signal box ("cabin") named for that place.

Richard