a study found that britons selling their properties refuse to admit the housing market has cooled and mistakenly believe they are sitting on a goldmine .
buyers must now increasingly treat asking prices as a starting point for negotiations as sellers demand silly prices , it is claimed .
sellers are now wildly over-valuing their houses by around £ 74,000 -rrb- .
while average sale prices are about £ 207,000 in the uk , advertised asking prices are typically £ 74,000 higher at £ 281,000 .