Leech & Sons shotguns were generally well made guns although I'm not 100% certain if they actually made their firearms or had them brought in from other makers back in the day.
W Darlow was a gun maker as well as a retailer. It is impossible to give a value with the information provided. Good condition doesn't describe anything, especially when dealing with old guns. Are the guns still original or have they been refinished over the years? Are there any cracks or repaired cracks? How is the checkering, has it been poorly recut? Have the guns been restocked. What are the barrels like--have they been cut, are they badly pitted in the bores, do they have bulges, have they been honed out leaving thin barrels? Are they damascus and, if so, what grade of damascus? Are there any dents or loose ribs? Does the action lock up tight. Do the guns function as they should? How ornate are they? These are just some questions that need to be addressed. They could be 2 or 3 hundred dollar guns like many of these end up being or they could be worth close to a couple of thousand. We need pics and more information.
I might also add that the market for these old guns is extremely soft right now and even worse in Canada. Also importantly, you buy the gun, not necessarily the name that is on it. And the big factor in all of this is condition. People often see these old guns and figure right away they are worth a few thousand dollars. They might be worth 3 thousand dollars but that's after spending 4 thousand to get it there. A gun that say,could have a 3 thousand dollar value but needs about 3 thousand dollars of work should be about a 3 hundred dollar gun when buying it.