The Nationwide has been producing quarterly statistics for UK House Prices for donkeys' years and you can access the data here:
http://www.nationwide.co.uk/hpi/datadownload/data_download.htm
It goes back to at least 1991, and the data is split both regionally and by house type (terraced, semi, detached etc). You can select what you want and download the data as MS Excel worksheets. I'm not sure that this data would be accepted by the Valuation Agency though, as 'evidence' as to waht your band should be, though it is a good starting point for you. In SE England, average prices fell by about 15% from the start of 1991 to the start of 1993, and did not regain their 1991 levels again until about 1995. What drove the rapid rise just prior to 1991 was the Government removal of some tax-break on mortgage interest (can't remember all the details - some like Dzug or Factor30 might remember).
But if I was spoiling for a fight with the Valuation Agency, I would use the data available at the VOA website which shows the council tax bands of all the houses around the one I'm comparing to, by postcode.