I think what I am trying to say is that places like York and Exeter have a disproportionate number of people going into the city centre for reasons other than working in an office or shopping compared with Birmingham and Leeds, so will remain prosperous (and as a result a more desirable location for the remaining offices).Not sure why there is this view that York is a small city (it's often stated) - depending what you include, it's getting up towards 200,000 people. So not Leeds or Sheffield, but by no means a small city. I lived there for years and the city centre has become a lot less diversified than it was a couple of decades ago - any time a business of any type closed, it seemed to become a restaurant or bar. Locals tended to mostly do their shopping in the out of town shopping centres. I'm back there with work often, but I think I've only been into the city centre once in eighteen months.
I think Leeds might actually weather this OK - it will remain the regional capital and the main shopping centre, and I remain unconvinced that working from home is going to remain in favour long-term with the type of legal and financial businesses which are big employers in the city.
It's probably going to be the second-rank cities and large towns which really get hit hardest. It was already noticeable before this - look at the centres of places like Bradford, Hull, Doncaster, Oldham - they are getting quite run-down, with a lot of empty shops. I've been to Sheffield a few times recently, and that's quite noticeably going downhill too - empty shops even in the main shopping streets. Meadowhall didn't do it a lot of good, but up until recently the city centre generally seemed to be doing OK.
I agree that places like Oldham have a fairly grim future for the reasons you state.
I think it will start to become a serious civil cohesion issue when the current situation of city house prices and rents being typically higher than suburban/market town/rural house prices reverses and people find themselves trapped in what increasingly resemble ghettos.
That divide is already manifesting politically in England with, increasingly, non Tory MPs being restricted to the big six cities (London, Birmingham, Manchester, Liverpool, Sheffield and Leeds) with Tory MPs elected in most other places (even places like Blyth) and Labours magority in the seats they still hold outside the big six cities, except a handful of seats in small university cities like Cambridge Canterbury and Exeter.