Thank you Lustrousstone for the information to add into my small but growing list.
It's a very interesting possibility about Newton le Willows because in the 1870s the family (name WALTON) return there and open a flint glassworks on the opposite side of the road to the original crown glass works at Newton le Willows. However, there's a problem in that the Newton crown works didn't open until 1832. And it is not very likely that the brothers were working in crown anyway, as they were flint glass makers.
It's a good argument that the girls were in service, perhaps in Warrington where the brothers might have worked for Bank Quay. I used to wonder if they were in service in Stourbridge where the brothers were born but perhaps the copy-cat Liverpool weddings, same church and within a month of each other, suggest the brothers were working there.
Thanks Neil for the Joyce references. Don't know why "Newton Thatto Heath" is listed like that. Perhaps it's an old name, because Thatto Heath is some miles from Newton, if that means Newton-le-Willows.
Have also found in Hajdamach's British Glass 1800-1914 that Hawkes Dudley Flint Glass Works had a 7-pot furnace in Liverpool in 1803. And a directory of 1827 says that Bank Quay had some sort of premises in Liverpool itself, but whether this was a glassworks or warehouse or office is not indicated. However the Inchicore website has a terrific page on Bank Quay, from which it seems that Bank Quay indeed had a warehouse in Liverpool, from 1767 in Old Church Alley, Liverpool, later Water street.
Going back to Steele & Foster in Argyle Street Liverpool 1825 (flint), I think that where there was one, there were probably others.
Great progress. Thanks to all.