Yes. And in addition purchasing power doesn't really capture the fact that £1 in 1843 can only be exchanged for the goods and services of 1843. For example
So is comparison at all sensible? Inflation calculations use a basket of goods, but when superior goods are substituted (e.g. light bulbs for candles) the comparison becomes less valid. Over 178 years, the accumulation of substitutions makes quantitative purchasing power comparisons much less meaningful.