Canvasback, I can see where your search for European guns, other than Spanish guns ( some great underappreciated guns here ) and old Belgian hardware store guns bears little fruit in Canada, but if you know what quality looks like, they can occasionally be found. I go to about 4-5 medium and large gun shows in BC each year with tables at 2 or 3 and I'm always examining any gun with two barrels that I see. On average here I see at least one or two, maybe more, really fine European guns each year, scarce and very random but they are there. These are mostly Belgian, German, Austrian in origin and with names unfamiliar to most, including me, but the quality is unmistakable. And this isn't counting drillings of which there are always fine examples at every show, usually going begging. Here again almost nobody has the specific knowledge on these guns so some real gems sell at give away prices.
I think Canada is traditionally a country of riflemen and other than regional interest, field shotguns other than for waterfowl has always been low. This translates to retail stores, their products and the customers they serve. Demand for fine side by side field guns is very low, stocking prices are very high, the business and therefore the interest just isn't there. The average store is just selling a product, no different than bicycles, fishing rods or potatoes. The employees or even the owner have no interest in or knowledge of old guns, anything that requires technical expertise isn't in their job description so they mostly avoud them. As you know, the barrels are the most critical part of these old guns and to acquire the measuring tools, learn how to use them, gain the experience to apply this knowledge takes years, interest and a large financial and educational investment. Most have no knowledge of nor understand the significance of Proof. Only a huge store with access to a qualified gunsmith, like Ellwood Epps or a specialty business like Vintage Doubles in Wenatchee Washington ( just a half day drive south of me) have these resources. None of us on this thread would dream of buying a gun like these on line, based only on a few pictures, a verbal but uninformed description and hope. I think TEC, unless they can properly vet their English guns are doomed to disappointment. One pitfall that I immediately see with these guns if they have been imported from Europe ( like the Swedish buyback) is that many may be out of proof, maybe far out. These can't be sold in Britain or Europe and the default is to sell them to North America, they don't know and don't care, if it goes bang they will buy it.
Regarding the spreader loads, I make my own and I'm very pleased with the results on paper and in the field. The only way to really know is to pattern several different ones in your gun.
John, I wish you hadn't mentioned that little Wilkes! You know I'm trying to quit.