just a quick interest why do you need to know, or is it just interest?
I dont think you can tell, If you were or knew the original owner on the log book they could tell you but other than that I dont think you can get the information. Moto Morini may have details of what dealer it was supplied to as new from the frame number but it wont tell you if it was registered by that dealer in that country or sold by them unregistered for import somewhere else, its frowned upon now but it used to go on a lot in the past, some dealers would trawl Europe for models difficult to get here, then buy abroad and bring back sell as a new bike unused and you never knew it was a grey import. Even if there were difference in the spec between UK and Non UK versions there is no guarantee whats been done to the bike in its life time.
I have a Laverda 750 sfc when insuring it, I was asked if it was a factory imported uk model, has it had any modifications? My reply was its a 1976 bike I didnt see it new I have no picutes and I have only had it 1 day having bought it from the widow of the the previous owner who died suddenly so I cant ask him, I dont know, and I cant find out. They didnt like it but had no choice but to accept it.