In terms of the wealth of both society and the average shooting man, I'd say the golden age was the 1890s to 1914. After the war, the UKhad gone from the world's greatest creditor to one of the debtors. Many men had seen all they wanted to of rifles, many, many more were simply dead or incapacitated, and the 30s were tight all round economically.
By the 30s the reaction against the "rifles and bayonets" mentality of the WWI generals, and their stubborn resistance to automatic weapons, meant that the baby of marksmanship and sniping got thrown out with the bathwater of "bayonets" and all that. In the late 30s as war became more and more obviously on the horizon, there was a bit of resurgence of interest in marksmanship and sniping, but in the military, automatic weapons were the "in thing".
The lesson wasn't really relearned until later in WWII I suspect, from the comments of Shore and others. Everyone was thinking about mortars, machine guns and the like. After WWII, more of the same as after WWI, perhaps counterbalanced then as well, by some who were introduced to shooting in the military and "took to it".
Lots of P14s and Mausers on the ranges in the 50s, 60s and 70s. Still mostly Lee Enfields I suspect, but not really the "golden age".
The only interloper to steal the Lee Enfield's thunder before WWI was the Ross.
That's my $.02 on it.