Now we're talking... land registry figures - much better than banks own indices. But I don't agree with the conclusions here; I'll explain why:
Imagine a fictitious village which comprises of a mansion, a house and a flat. In January, the mansion sells for £1M, the February the house sells for £500k and in March the flat sells for £250k. "Newspapers: Oh no! Property prices are down 50% month on month since the start of the year!". Suppose they were sold in the opposite order "property prices are rocketing!".
The point is that (especially with very thin sales) the distribution in the types of properties sold has a huge impact on whether you conclude prices are rising or falling. In particular, the transaction of high-end houses has a strong impact on the conclusions of an "average price" type analysis.
Suggestion:
'Average sale price' is any particular period is fickle measure of valuation changes. The correct analysis is on properties for which there have been two sales within, say, the last 10-years. This gives a firm handle on how the value of that property has changed. Repeat that analysis across all properties, and a different picture emerges.