Pete, there's another site which is very useful: https://www.measuringworth.com/ukcompare/
It allows you to compare past and present prices in a number of different ways; inflation, purchasing power, wage comparison and so on, and gives some idea of the best measure to use.
For example, I have a Ruddington catalogue from around 1952, which shows Bedford O types selling at, I think, £25 each. I found it interesting that in wage terms, that was almost exactly what I used to see Bedford TKs sell for at Aston Down in the '90s.
As an example, the Fodens that I've commented on in the past come out around £35,000 in RPI terms, but £92,000 in terms of the proportion of an average weekly wage it would take to buy them (probably the most meaningful), and a frightening £135,000 in terms of GDP per capita income!