I can spell, eventually. See!!! smile
But enough about me, there are other excellent books that while they don't concentrate on the sidelock they do list all of the various English patents throughout the developement of the breech loading shotgun.
'The British Shotgun" in 3 volumes
by
I. M. Crudgington and D. J. Baker

http://www.amazon.com/books/dp/1846891175

Great information written by excellent writers!!