According to The Telegraph there has been a blunder in the council tax bandings, that may mean that many people may be entitled to claim a rebate.
The article notes that "hundreds of people are receiving money back from local authorities after challenging the council tax banding of their properties".
Seemingly many of the 1991 valuations were performed by estate agents who would just drive past the house, without so much as "poking their noses round the door".
You can check what your neighbours are paying on the Valuation Office Agency website (www.voa.gov.uk), which gives the band for any house in the country.
If there is a discrepancy, you can contact your local council and ask them to look at the banding.
However, be warned, there is a chance that may increase your tax banding!
I had someone round from the VOA yesterday, and will publish the result when known.