I'm not sure it's true that Labour's northern support are leave-voters.
Well, my town voted 83% leave. I'd say that's fairly committed given that's more people than voted labour, even in the Socialist Peoples Paradise of Sunderland.
most leavers are either Conservative voters or traditional non-voters.
That's only true in the south. Up North and in the midlands most leave voters were labour voters; they had to be because there weren't enough Conservative voters to deliver those mandates - many many brain dead red constituencies.
Though it's also true that I think Labour held most of the top ten remain voting constituencies in England in 2015 - as well as most of the top ten leave ones.
Yup but the remain ones are mostly London(ish) with a high percentage of youngsters, which was my point. Northern heartlands Vs young south - the party is trying to play each off against the next in a blind pursuit of power with absolutely zero idea how to reconcile that once they're in #10, which is all they actually care about.
Though as you say, none of this privatisation can be legal if it reaches the ECJ
Legal or not they simply can't afford it. Parliament can't set the prices because those firms are owned in the main by private sector tax payers in their pensions. Nationalizing them at anything less than full market rate would be theft of our pensions, which simply won't wash.