It’s one of those Pub debates which my colleagues are currently arguing about.
Various semi-humourous suggestions like “The M4” or “Watford Gap” – but practically and culturally speaking? I’m not sure. I know that when you get to Leeds there’s still a whole lot more “North” above you.
As a Midlander I’ve always mentally drawn a line approximately running from Wrexham to Boston:
…so that Stoke is “almost north”.
But I wonder how accurate that really would be perceived to be?