The Land Registry website has a House Price Index tool that allows you to put in your postcode for a single location (or multiple locations) an find out the average price of different types of houses in your area.
The tool can be accessed by clicking 'House Prices' in the top left green box on the screen I linked to then click 'Search Index' in teh orange box in the centre of the screen , then click the 'Single Location' button and press next.
Then enter your postcode or select a county or town and press next. The pages after that allow you to choose different types of report, house types and date ranges.
I did a test using Cambridgeshire for September 2002 compared to August 2009.
The average price for all types of houses was £130,369 (Sep 2002) versus £166,863 for (Aug 2009).
That is a rise of 28%.
The Land Registry figures are based on actual transactions rather than estate agent asking prices so are a reflectve of what is really happening in the market not just unrealistic owners demands. The Land Registry price indices have typically lagged and are lower than the indices based on asking prices (Rightmove) or mortgage advances (HBOS/Nationwide).
I use the Land Registry fggures to work out how much a house should really sell for. I take the price any gven house was last sold at and then apply the percentage increase/decrease for that area and type of house from the Land Registry.
The price a house last sold at can be got from Rightmove and various other websites.