Well.... densify town centers and develop better public transport, then. (It's basically only possible to develop good public transport networks across cities if you have a lot of "heavy public transport" users in the center of town, otherwise it's just not financially possible)
The UK is very unusual in having a situation where the capital city is the only one in the whole country that has proper public transport.
In most European countries, cities the size of Leeds, Birmingham, Manchester, Sheffield etc. have much denser urban cores and good public transport, including a subway in most cases.
The attitude in the UK, that somehow decent public transport is "inherently" only possible in London and couldn't possibly be done elsewhere, is just so weird from a global perspective.
I get that I am sounding like a stuck record on this issue, but it's probably the only way if the UK wants to have decent town centers. If you don't have lots of people living at the center of cities because the vast majority of people live in houses in the suburbs, deserted town centers are almost inevitable, because you don't have a critical mass of people living on the doorstep of the town center--and the suburban dwellers will nearly always choose out-of-town shopping malls (because they have to drive anyway and out-of-town center are always, always going to beat the town center in terms of car friendliness. Because they have more space and always will do).
The UK needs to build shitloads of housing anyway. You can either build in town and densify, or you can concrete over a load of woodlands and meadows in what is already one of the world's most nature-depleted countries; your choice!