Thanks both - I've been out and meant to respond to some of DK's points but I think Paul has covered everything I was going to say.  Except I did some digging around about valuations and so on...

The Land Registry deals withsomewhere north of 5 million transactions per year that involve a valuation with which both principals must be at least happy enough to do a deal - either a mortgage or a purchase.  So that's about 20% of the housing stock.  Then there are the 30% of households who are rented anyway and therefore know exactly year to year what their landlord thinks the property is worth.  So something like 50% of the residential sector is valued every year by the market.

Given that the Oxfordshire study showed that a satisfactory result for occupiers could be achieved by valuing about on in ten properties, the market data already seems substantially better than that.

But, DK, one other thing - part of the problem at the moment with our strange relationship with land is precisely that owners aren't more aware of the "passing rent" value of what they occupy.  The level of location rent on a site is a financial expression of how much one's occupancy of a particular site is breaching "Locke's Proviso" (from Robert Nozick) and therefore harming other possible users of that location.

Surely it is a fine libertarian principle that people should compensate others for the harm they do them?