Kevan: A Webley & Scott single barrel shotgun is certainly an interesting find. You make no mention of gauge, but if it is a .410 then it is most likely a converted rook rifle. On the other hand if it is a 12 gauge then it is likely to be the Model 100.
The Model 100 was introduced in 1914, and was produced in a few variations up until the early 1970's. These guns had a single protruding hammer (like the Cooey). Between 1915 and 1929 they made a trap gun variation. Examples of the 100 with both 2 1/2 and 2 3/4 inch chambers can be found. It affects the value if a 2 1/2 inch model has been bored out to 2 3/4 inches. A good gunsmith will be able to tell.
At first the gun was based on a Baker patent, but the design was improved by Webley engineers throughout the 1920's. Another variation, the model 1100, was produced in very small numbers using a hammerless sidelock.
Webley & Scott never made a bad shotgun, but they did run the gamut from basic utilitarian guns to best quality models. Knowing this examples original grade, year of manufacture (which might be found in the proof marks) and its current condition would help. Any possibility of pics?
I have no idea how useful a single shot shotgun will be to you. If the gun is a trap variation (and in good shape) it would be a real attention getter at the club. The game variations are less successful at trap, but are excellent for early season ruffed grouse where more than one shot is unlikely. Either way they are interesting guns to add to a collection. If it is in good shape and you like it, jump on it!
Sharptail