If such a converter exists in a meaningful fashion it would have to look at the same shopping basket of course.

Inflation is a bugger to calculate. The arbitrary government calculators never relate to peoples' experience anyway. Flat low inflation over recent years sounds plausible if you look at property prices in The North but laughable if you are buying in The South East. Conversely, therefore in The North, the percentage of your income spent on electricity gas and water has increased more than some poor bugger with a London mortgage.

The cost of luxury goods has gone down but so has the ability to afford them.

It isn't just the shopping basket, it's also how relevant the shopping basket is.