I'm not arguing where the a Labour heartlands are but I would state that support is largely found in the large urban areas whilst the Tories controlling the countryside, even in the North. Clearly you would find more 'Harrogates' down south as the population is bigger but there are plenty of places like Alston, Brampton, Hexham, Richmond, Northallerton, Beverley, Morpeth, Alnwick, Ormskirk etc etc who vote Tory (or Lib Dem occasionally). So I guess my point is simply generalising areas i.e. North and South, even Northwest and Northeast isn't the best way to contemplate forms of devolution in England. I don't know what the solution is but I personally don't feel England is as divided as you make out.
But it's the North of England, Wales and Scotland where the Labour heartlands are. As for Salisbury it may have more in common with Harrogate, but there's only one place like Harrogate in Yorkshire, there are plenty of places like Salisbury in Southern England, Winchester, Bath, Chichester, Devizes, Oxford even. I once traced the route of the defunct Somerset and Dorset Joint Railway from Bath to Blandford Forum, it truly is a different world! For one thing (and I know you'll contest this) "the South" for the most part is where all the money on defence spending goes. You can't help but notice the plethora of roadsigns with red borders once you leave the M1 at 15A and take the A45 towards Brackley. They're everywhere. In the North you see a few round York, Ripon and Catterick, but that's about it.
As for the MOD sites, there is a reason why there are Army sites scattered around the South than the North; the direction of threat! However, that is changing to a certain extent with British Forces Germany returning back to the UK (Stafford, Catterick, East Midlands and Scotland growing substantially by 2020) and also the RAF is configured far differently with most of their assets located along the Eastern Coast from Norfolk up to Lossiemouth in Scotland.