Not sure that's quite the case down here in London. I live in Newham and while the papers bang on about a lack of room we have plenty. There are dozens of derelict buildings and stretches of land here that could be built on but the owners are just sitting on them. Why? Some speculate because the land value keeps rising there's no reason to waste money building on it. At the same time the council is seeing fit to bulldoze hundreds of council houses and replace them with brand new flats, but less than they bulldozed. Go figure.
Agree somewhat with moving things north though, the balance between the south east and the rest of England needs to be looked at. Or at least the north needs to start being more competitive.
Roughly in reverse order:
The North is already much more competitive. For a start, house prices are a lot cheaper. Many people live in the South because they want to be where the money is, and many companies set up there for the same reason.
Brown-field sites are hated by building companies, because every one tends to be a can of worms. Or toxic waste. Or old unmarked landfill etc. And the price that can be got for any house built there is far lower. Building companies are not charities, they want the money, so they want the bigger profit of green-field. But yes, a lot of big properties are parts of things like pension portfolios. In many cases they have changed hands so often that it's all but impossible to work out who owns them.
Councils don't build houses because all that does is subsidise the right-to-buy, one of the most stupid political ideas of last century. OK, it was a brilliant idea politically, but disastrous for the housing market in the longer term. Flats are OK though, because almost no-one wants to buy those. Not until the area gets gentrified anyway. And any idea that councils might be able to forcibly buy up unused property is political suicide for the foreseeable future.
In response to an earlier comment about large bits of the South-East being empty, or at least appearing so. Yes, it appears so. Trouble is, that's all lad which is never going to be allowed to be developed. Let's start with the golf courses and occasional race tracks - there's no way on earth those will ever be developed. Then there's the farming land. In theory yes, in practice the political fallout of any but a very small amount being developed is too much. Ditto woodland. Which doesn't leave much.
Finally, don't forget the obvious: the Tories want a house price boom, no matter how much they deny it. They still have no policy for the long-term economy beyond people borrowing money on the back of increasing equity and spending it in shops. It worked last time. To be fair, neither do the other two parties.
We certainly should be looking to redistribute economic activity more evenly around the country.
