Good picts, they tell a lot.
First, that type of action is called a "back" action, with all the internal springs and moving parts behind the hammer. About the only US made handgun of the period you see with that type of action is the Deringer type, the one John Wilkes Booth used to shoot Lincoln, but there could be more...
In the mid 1800s a lot of quality commercial, but usually NOT military handguns, made in Europe had that type of action, so it appears to be correct for your "London" stamp on the barrel. Manton for example made a lot of high-end target pistols at that time with a "back' action, but that isn't a "target" pistol, it's an "everyday carry " gun...
Most percussion and flintlock actions had the hammer in the "middle" of them, with springs in the locks in front and in back of the hammer...which most military guns had too.
That also tells me it PROBABLY is not a "conversion," i.e., not originally an even older Flintlock converted to percussion, but I could be wrong....but I also think this because the barrel is held by a wedge and tenion, most but not all earlier flintlocks were "pinned."
I'm still interested in the caliber and if it's rifled, but what I can see from the picture is a pretty decent example of a period percussion gun of the mid 1800s, probably made in the 1840s or 1850s, as a "pocket" pistol, as opposed to a holster or "horse" pistol, which usually had longer barrels.
It has enough "extras" like the end cap on both the butt and forestock, as well as some of the inlays and thimble and the like, that it was a quality gun in it's day, not your "run of the mill" hoodlum's or "Hardware Store" gun...
It's condition looks to be pretty typical of the period too, not too abused or rusted, what from the pictures looks like original finish in good shape, it would probably from what I see be considered"G-VG," maybe even "Fine" condition as an antique gun, depending on whether the action works or not. Does it?
I am NOT a collector of these, so somebody here MAY know more as to it's value, but as a WAG, I'd guess $400 to $500 might NOT be out of the question.
Again, more research, might turn up better information, that could double or triple that price, or else it could also halve it if 'Taylor" made THOUSANDS of them and they all survived, but I doubt it.
None of the books I have show any "Taylor" guns of that era in either the European or American sections, but that doesn't mean anything especially, there were MANY "obscure" gunsmiths that made quality weapons during that time period, in London.
I STILL think that ramrod either isn't original or it was broken or both. while it shouldn't be as long as the entire barrel, if you stick it down the empty barrel the end should be at least NEAR the muzzle...(be careful, run a longer brass or alluminum rod down the barrel first to see if it might be still loaded, MANY of these old muzzleloaders are still loaded, and STILL might go off if a cap is fired on it!) If it's UNLOADED you should be able to feel the rod "clink" against the steel base plug, if it doesn't, or if it doesn't go all the way to the base plug when you mark the muzzle end with your finger, and then pull it out and lay it on the barrel to see where the end would be, it MIGHT be loaded...and don't use the ramrod for this test, if the barrel has any dirt, crud or corrosion in it, the actual ramrod, MIGHT go in all the way and stick, which then may be a pain to get OUT!
If I have time later in the week I will start some Internet research, I enjoy doing that.
You can start too...just go to the bottom of this page where you see the "Google Search" and type in something like " 19th Century London Gunmakers" or "Taylor Percussion Pistol" or something similar and see what pops up! That's usually how I start anyway, you might be surprised what you find!