Limited disposable income in many northern areas. Towns there seem to be dominated by book makers, charity shops and money lending places
Given the enormous cost of housing in London and the South East, I would be surprised if median disposable incomes were significantly higher than in Leeds, Manchester, Liverpool, Newcastle etc.
Or perhaps they believe the Mumsnet myth that there are no jobs outside London and if they are they are all zero hours NMW gigs (clue - we still have doctors, nurses, fire fighters, teachers, accountants, etc in the North and they are paid a wage that can allow a comfortable lifestyle, ability to purchase an entire house and have disposable income too).
OP I agree, it is short sighted and unfair that the likes of Uniqlo concentrate all their shops in London. I do shop with them. I simply order everything I like the look of in multiple sizes and send back 80/90% of what I order.
If that doesn't suit them, they can damn well put a shop in my nearest city and I will go there, like most other people who live nearby
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