The Land Registry data is the "master set" to judge what a house is worth.
Until you know how many properties are excluded from its data
www.landregistry.gov.uk/professional/market-trend-data/house-price-data-exclusions
any involving companies (like buy to lets and overseas oligarchs)
any sold at auction or reposessed (because they were overvalued)
any right to buy property
any shared ownership property
etc etc
so all the poor saps who think the market is holding up OK are being mislead by the Governments own department