Here are some titles of books that you might be able to Inter Library Loan from your local library:

Gunmakers of London, 1350-1850, by Howard Blackmore, published in 1986

Game Guns and Rifles: Percussion to Hammerless Ejector in Britian, by Richard Akehurst, published 1983

1998 Standard Catalog of Firearms: The Collector's Price and Reference Guide, 8th edition; Ned Schwing (ed), published 1998

I am interested in the outcome, too.