I have an unoriginal theory - there's going to be a housing crash pretty soon. It makes sense. If you imagine homes in England to be like loaves of bread at the supermarket, when all the cheap bread's gone, everyone who can afford it is forced to buy the expensive stuff. Those who can't wait for a new supply to come in. Then if the new supply is inadequate there has to be a price drop.
Look's to me like all the cheap bread's gone!