It starts with the furtive surfing of property porn, a late-night lust for rose-covered cottages and tumbledown farmhouses and the acres of Northumberland available for the price of a small suburban London flat. Before long, you’re daydreaming on the tube about keeping chickens and letting the children run wild in the woods. But if moving to the country is the secret new year fantasy of many living in the capital, they should know this: if you go, it may not be easy to come back. And not just because you’ll be left for dust by galloping London house prices.

There is a bitter, ugly grudge brewing between capital and provinces that goes beyond the traditional town v country grumbles. It was hanging in the air this week at Ed Miliband’s Manchester press conference, when a reporter challenging him over the NHS was heckled with shouts of “get back to London”. (London has some of the longest A&E waits in the country, but is still seemingly synonymous with an overprivileged la-la land where everyone goes private and burns 10 pound notes for kicks.)

And it was there too in the Scottish Labour leader Jim Murphy’s southerner-baiting suggestion that extra Scottish nurses be funded via a mansion tax levied mainly on London.

This row is phoney, obviously. The proceeds of any mansion tax remain earmarked for the NHS: all Murphy means is that the extra money automatically generated for Scotland under the Barnett formula, whenever spending rises in England and Wales, would go on healthcare in Scotland too.

In that sense, Diane Abbott, a London Labour MP, was right to call it a cynical bid for Scottish votes. But all those MPs in the capital reacting like shocked maiden aunts are arguably chasing votes too, from those Londoners who increasingly view the rest of the country as losers begging for handouts. So much for the misty-eyed togetherness of last year’s No campaign; so much for never taking the union for granted again.

Perhaps all this reveals is that devolution has turned politics into a fiendish Rubik’s cube, where you can’t complete one face without disrupting another. After all, Labour is in effect fighting three different elections in one: Westminster this May, plus the London mayoral and Scottish parliament elections next May. But it also says much about the place London occupies in the rest of the country’s imagination, and vice versa.

Having moved from the capital to rural Oxfordshire five years ago, I can’t deny the distance between them is more than physical. Life is slower here, mindsets more conservative, with a small and sometimes large C. But it’s more than that. The leap from city to village is like the shift from capital letters to lower case in a text message; like the difference between a brash, sprawling Tracey Emin installation and her beautifully delicate line drawings. The themes are the same, but muted and less urgent.

There is a particular sort of London-ness I sometimes miss, something intangible beyond theatres and restaurants and the buzz derived from any big city. London is different. But not to the point of being a foreign land; not to the point of being forced to choose sides. Contrary to popular myth, provincials don’t all hunt foxes and wear flat caps any more than Londoners are all bankers who own £2m houses. We’re just more likely, on both sides, to know people who do; and to regard them at least as fellow humans, not aliens. And it’s this empathy that the mansion tax row lacks.

It would be undeniably harsh to force pensioners who bought modest family homes 40 years ago, only to find themselves with post-gentrification goldmines, to pay an annual mansion tax they can’t afford. But if liability could be deferred until death, then this group would effectively be on a par with the lottery winners they resemble, who aren’t taxed on their windfalls but on the fortunes they eventually bequeath.

Which just leaves the London question, now nearly as sensitive as the West Lothian one, about who gets the money; who benefits from the capital being so much richer than everywhere else. And that’s just an age-old argument about redistribution, about what the haves owe the have-nots when sometimes, without the latter, the former wouldn’t actually have much. Somehow London has become lazy shorthand for “have” and the provinces for “not”.

It’s true that 80% of any mansion tax would be raised in London and the south-east, not because London is being somehow punished but because that’s where most of the expensive houses are. Guess what: a hefty slab of higher rate income tax comes from London too, because that’s where many of the richest people live. (Nearly a quarter of London taxpayers pay higher rate tax; it’s fewer than a tenth in the north-east.)

Nearly half of UK capital gains tax comes from London and the south-east, for that matter. What next? Demands for all that dosh to stay down south too? Should it be “finders keepers” for the billions generated by the City, or Scotland’s North Sea oil money – conveniently forgetting that we all bailed the banks out, or that the Scottish oil industry would like Downing Street’s help to ride out falling oil prices?

London is indeed the engine of the national economy; that’s rather the point of a capital, even if Britain has arguably taken it to unhealthy extremes. But the lesson of the banking crash and the near break-up of the union must be that nations are greater than the sum of their parts.

Talk of London seeking independence from the slack-jawed masses is all very witty, but good luck feeding yourselves, chaps, off what you can farm in Hyde Park; good luck keeping those schools open, streets policed and tills manned without the millions slogging in on commuter trains. See if you can maintain that cool, creative buzz without talent drawn in from provincial towns.

But in return, those of us outside the capital can’t blame everything that’s wrong on rule by some remote, hedonistic metropolitan elite that doesn’t understand. It’s a line seductively peddled by Ukip everywhere from the shires – where the rallying cause is housebuilding imposed on rural communities by townie planners – to struggling northern towns, and it’s toxic.

London and its hinterland need each other: given the ebb and flow of people from one to another over a lifetime, often we are each other. Nursing mutual resentment can only do us harm.