I agree that the idealised Labour voter does still exist in large numbers, and you've got to remember that Scotland is part of that "north" too, and my family up to my grandparents would class themselves as diehard Labour types who vote Labour primarily because that's what our "kind" did (my grandad, a beer delivery driver in his day, even has a framed photo on his dining table of him meeting Blair).
But it's a dying demographic, both in the literal sense (touch wood for the old man) and also in the sense that many of them have less need now for what the left offers. People in their 50s don't need cheaper housing - they have mortgages paid up already and they'll be damned if the government tries to drive prices down. They don't need rent control. They don't need more graduate-level jobs or apprenticeships. They don't need lowered tuition fees. They don't need the freedom to travel around Europe to work or study. They don't need cheaper public transport, they've mostly got cars or they've got it free. They're getting older, they've not got much more they need out of life or the state, and in their age they grow a bit paranoid or embittered and worry about the stuff they read in the papers, which is primarily immigrants and the EU.
Labour it seems to me is stuck between turning back to try and claw back that demographic, or pressing on and trying to position itself as the party of tommorow's "working class", if that even will have any meaning in a decade.
In Scotland it's not quite the same as that, but traditional left-wing voters get picked off by the SNP because they're essentially a blank canvas type party which positions itself wherever on the spectrum is liable to attract the most Scottish voters, which right now makes them centre-left.