Drew, I would say that is a Flatcoat in the Thorburn picture. They were very popular around that time and the sort of dog a Gentleman would have.
I understand you have that exported programme over there called Downton Abbey; the one where as time goes on nobody gets to look any older. It shows His Nibs with a yellow Lab. A bit of bad casting. I don't think the Lab gets any older either! Lagopus.....
Lagopus, Downton Abbey takes place between 1910ish and 1930ish. Weren't labs developed by then?
As an aside I watched very closely during the one episode where guns were visible during a shoot. While not close enough to identify the guns by maker, all appeared to be reasonably highly engraved sidelocks, the type of gun I would expect those people to have been using. Made me feel better about potential historical accuracy.