I don't know. I suspect they would try to sell me whatever they have on the rack and say it is strictly impossible to import used firearms from abroad, wether true or not. I agree it would be nice to have access to imported used side by side shotguns from England, they have very good and renowned shotgun makers there, but the gun trade around here is not as enthusiastic as it looks to be in the States. It often looks more like a suffering business than a passion (I guess I should specify I am observing this in Quebec, I heard it is a little different in other parts of Canada); I often felt I was disturbing the guy behind the counter with average, normal, honest questions, nothing pointy at all, and, quite frankly, counting a very few exceptions, most of the people behind gun counters I spoke to knew very little about firearms, while a few pretended to be very cognizant, most of them didn't even really know what was behind them. A salesman telling a guy who had obviously never shot a center fire cartridge to buy a cheap synthetic 300 RUM for his first moose hunt and prepare to shoot until the magazine is empty is the kind of stuff I hear when I am in the store... Not "we should privately import great used shotguns from England", sadly.
As for the 28 gauge suggestion instead of a 410, well, the idea has crossed my mind, I don't think it is a bad idea at all, but I arrived to the conclusion that I want a 410. The wand feeling and very light weight are solid arguments to this regard, as well as is the necessity to better judge opportunities and take even better shots to bag game. I think the 410 ammo is also more abundant or more available than 28 gauge ammunition around here. It is not twelve gauge, but it can be found easily.
Also, I like to keep things simple (or at the very least try to do so) and foresee within a few years my heir accompanying me on a small game hunt. For now, my choice for his first firearm is a Chiappa double badger in the .22 LR and 410 bore combination offering. I like their sights and the fact they can be used as a single shot .22 at the range for shooting initiation and learning the fundamentals as well as a hand thrown clay pigeon buster at the same place to learn how to point and shoot at moving targets. Inexpensive, light and short, that weapon seems like a good choice for him: he shows a rather frail constitution. Recoil would be minimal in both its rifle and shotgun use. Both barrels would force good judgment and good shooting into a good habit. It is not bought yet, I am waiting to see if he shows any interest into the whole hunting and shooting game before I spend even a cent on this. If I was to buy it and find my son to loose interest afterwards, which would be sad, that gun wouldn't be wasted: I would happily use it sometimes, or it could be sold or given to someone who needs it without a cry. Anyway, as I was mentioning, simplicity in ammunition provision would additionally encourage me to shoot the same shells as he would. If I was to reload 410 ammunition at some point, sharing the same shotshells would be even wiser and could bring him too into reloading.
So, I stick with this idea of a 410 bore side by side shotgun in my not too distant future.