...and yet it's the reddish brown...
Which perhaps suggests than Brendan's list refers to those rebuilt, as opposed to those used for Courtaulds. So, probably the one I saw was not rebuilt, but was used for Courtaulds.... would that make sense? If the "C" prefix refers to Courtaulds traffic as earlier suggested, this would add to this theory.
It has just occurred to me that the spoil wagons, as far as I remember, had numbers beginning with "M". Obviously, then, "Magheramorne"?
Such us the beauty of research. Fifty years on, we learn something new every day.