It depends on what you mean by 'days gone by'. If you look at most bank's Websites, they regard historic information as being back to 2006! This report from the National Statistics Office http://www.statistics.gov.uk/articles/economic_trends/ET604CPI1750.pdf copy presents a composite price index covering the period since 1750 which can be used for analyses of consumer price inflation, or the purchasing power of the pound, over long periods of time. This page explains how these calculations can be made http://www.statistics.gov.uk/cci/nugget.asp?ID=22 copy
