What a coincidence. I just looked the Ashmores up today for someone else. There are two listed in Bailey & Nie - George and George Jr. in Darlaston (ca. 1854) and Richard in Wednesbury (ca. 1827-1855). These are two of the three famous black country lock making towns. The Ashmores were major exporters or suppliers to exporters and I suspect that they entered the market as the Ketlands were leaving it... I have no recollection of ever seeing an Ashmore lock on a completely British-made gun. Also, keep in mind that Bailey & Nie is based strictly on period directories so if a maker wasn't listed over a period of years, those dates do not appear. Thus, these are minimal dates... they could easily have a much wider time span. The fact that they were listed at all suggests that, like other aspects of the B'ham trade, they organized the production of gun locks - not that they actually made them themselves. From these dates it is clear that they were working well into the percussion period.
I am certain I have handled numerous NE guns, mostly flintlock militia muskets, with Ashmore locks. The locks tend to be of better than average quality. A date as early as 1827 is entirely consistent with this as percussion guns probably did not make a significant inroad into flintlocks for militia purposes until the 1830s. The gun I was asked about today was a NE flint musket.
My memory of the fake Ashmore locks is that they were much smaller than any of the original ones I have seen. I've owned several and seen many more and all were musket/fowler size. But... locks were made in standard sizes, usually referred to as "gun locks" and "pistol locks" (at least that is how they are described in shipping manifests) The "gun lock" is larger while the "pistol" size may also have been used on rifles. I am not knowledgeable enough about rifles to have a strong opinion on this but I have seen evidence of the importation of more "pistol" locks than I have seen evidence of pistols assembled from them.
