Mr E,
Your Westley Richards Martini with U stamp is ex-S Africa. Any ZAR stamps on it?
The rifle is probably a commercial sale to a burgher, or else a govt sale - a "£4 Martini" - that is, sold for £4 by the govt. of the Boer republics to citizens in the years leading up to the Anglo Boer War. The govt. sales tend to be marked ZAR somewhere on the receiver, but this is by no means the rule.
The U markings abound on S African Martinis from from the ABW, indicating that they were taken into the govt. strategic reserve after 1910 - probably during either WW1 or WW2 - it is not clear to me exactly when this happened. There was greater external threat during WW2, but greater threat of civil war during WW1.