The majority of A & N's double guns probably did come from P. Webley & Sons prior to the merger in 1897, and from Webley & Scott thereafter. They were almost certainly their preferred supplier due to volume and quality, but it's a mistake to assume that this was exclusive. Just in the last year I've seen A & N double shotguns and double rifles that records show came from Osborne, Westley Richards, and Saunders. Non-Webley A & N guns aren't that hard to find.

"Serious rifles have two barrels, everything else just burns gunpowder."