John, Good to speak the other day, as Our conversation was cut short, I was going to say If it was me I'd get a Uberti / Pietta 1851 Navy etc, to plink with........... a BP variation of a FAC doesn't take long........ as you have the original its another start to a collection, then its an open door to Section 7.1.....
The link below to the Westlake conversion of the .357 LBR I mentioned, I run this on Unique now instead of Herco, in fact my LBR runs on it and all my downloads run on it........ after looking for info on your London Colt I found a few youtube clips on folk making paper cartridges ........... very interesting as I may knock a few few up to try, normally I use glass vials which carry each charge for my Ruger Old Army ........
http://www.milsurps.com/showthread.php?t=34121