Greetings all!
May a viewer from across the Pond weigh in on this?
I have read and re-read this thread, and I have a hunch that Owlet/Hullet Hall was the structure on the west side of the present Cold Royd Lane, immediately south of the former railroad grade. It has been demolished and a new stone dwelling house erected in its stead.
My basis for this hunch arises from the lady's finding that the Howards were listed at Owlet Hall in 1841 and then Coldroyd in 1851.
The old house most often referred to as "Coldroyd" (and now "Coldroyd Cottage" according to realty ads online) stands at the top of the present navigable part of Cold Royd Lane, on the east side. It dates from no later than the XVIII. century (see Grade II listing per British Heritage), and it seems to have been a farmhouse originally. My immigrant ancestor John Broadbent dwelt there until he came to USA in 1839, and his family (North-Broadbent-Kilner) seem to have occupied that location from an early date (maybe even XVI. century???) until around 1917. These people were farmers as well as woollen manufacturers. That eliminates that building as "Owlet Hall."
The place I surmise was either Owlet/Hullet Hall or its replacement seems to have been a newer structure, probably from the XIX. century, and it appears in the well-known postcard view showing a train crossing the bridge over Cold Royd Lane. It seems plausible that, as these buildings were converted into multi-family dwellings, everything on the present Cold Royd Lane was enumerated as being in Coldroyd hamlet, and the Owlet/Hullet name disappeared.
Nearby, rather to the northwest, stands another ancestral hall, "Laverock," or "Laverock Hall"; but that seems to have a fairly well documented history under only that name.
What think you who know these places much, much better than I?
From an Observer in the Antietam Country of Pennsylvania.