[Jim McDougall]

Keith, in trying to locate the reference to Koln (Cologne), I recall reading this passim, but it seems this situation was in earlier years of the Solingen blade producing phenomenon. What was said was that while the blades were of course made in Solingen, they were sent to Koln for mounting, and that for some time German swords from these regions were termed 'Koln swords'.
This kind of circumstance happens in a number of cases such as with the swords of North Italy from various cities were collectively termed 'Genoan' as that was the port of export.

In the period in discussion which is centered in later years of 18thc. the focus has been on fully decorated blades being exported into England.

What I just found is from "The American Eagle Pommel Sword:The Early Years 1794-1830", Andrew Mowbray, 1988, p.55;

"...almost all of the earliest eagle pommeled swords cutlered in London used blades imported from Solingen by any one of a number of local brokers specializing in the German blade trade".
It is noted that Runkel was the most important, however there were a number of others with family in Solingen furnishing them with blades as well.

Further noted, "...commodity quality Solingen blades were at this time, almost ALWAYS of simple blue and gilt decoration, sprigs amidst hastily outlined crude panoplies of arms. Because of their non nationalistic designs, this style of blade could be sold widely throughout Europe".

While the references refer to the swords being exported from England to America by London cutlers, the important notes are to the fact that Solingen was supplying fully decorated blades to England and other nations in the period 1790s-1815.
The references to these blades apply of course to officers swords, and it is noted that the examples with decorated blades were likely from Solingen, and with plain blades were most probably from Birmingham.

I would note that the blades by Thomas Gill, who initiated the so called 'sword scandal' in 1790s was a Birmingham maker, as was James Wooley who both produced officers sabers without the blued and gilt decoration typically, and used their own blades, as far as I have known.
The 'scandal' was the claim that English blades by Gill, Wooley,et al were not only as good but better than the imported German blades. Runkel furnished German blades for the testing.

It is unclear whether artisans decorating the Solingen blades were there or in nearby Koln, but possibly that cutler industry indeed remained as before for fully decorated blades.

For listings of sword makers and cutlers in England 19th c.

The source by Mowbray (op. cit.) has two pages of names but possibly incomplete as the focus was on exports to America.
Others:
"Swords for Sea Service", (2 vol.) W.E.May, P.G.W.Annis, 1970 most comprehensive
"Swords and Sword Makers of England and Scotland", Richard Bezdek, 2003
" London Silver Hilted Swors", Leslie Southwick, 2001

These are most useful compendiums, but it sounds as if Mr. Langham is doing a great deal of primary research beyond these sources. These, especially 'May & Annis' (the venerable standby used since the 70s) have been the 'go to' sources on this topic for many years. Mr. Langhams work will be a welcome and important addition.