Even then, Allan, the Scottish vote didn't change the finally elected Westminster government. In 1950, Labour had a majority of 5 and without the Scottish vote there would still have been a Labour government with a majority of 2: in 1951, Conservative majority of 17, without Scotland majority of 16: 1955, Coservative majority 60, without Scotland majority 61: 1959, Coservative majority 100, without Scotland it would have been 109 so in effect since 1945, actually, Scottish MPs have never turned what would have been a Conservative government into a Labour one or vice versa.
In 1964 and in 1974 Scottish MPs have given Labour a majority they wouldn't have had from England/Wales/NI alone but it wouldn't have changed the elected government as Labour was the largest party and it would have gone to a hung parliament.
In the 2010 election Scotland sent 41 Labour MPs, out of 59, but we still got a Conservative led government, so to sum up, the Scottish vote, whether overwhelmingly Conservative or Labour makes no difference to the government in Westminster.