Someone pointed out to me that the Lib Dems have been talking about empty homes: "There are over 760,000 empty properties across England which are no longer used as homes but can be brought back into use with some investment."
According to CLG, only around a third of these homes (c300,000) are empty for more than six months. The government target is for 240,000 new homes to be built per year.
The detailed figures are available here. They show that only 28,000 of these long term empty homes are in London, with another 36,000 in the South East. That is, in high demand areas, very few houses are empty.
Using empty homes will (sometimes) make sense. But it will not do much to solve Britain's housing problem.