At the time of writing, CPI is running at 2.4% per annum and RPI at 3.3%.
My results are tabulated below with a few following notes on the methodology and values used etc. I've hidden the columns with the actual sums spent, and am just displaying the percentage changes from 2017 to 2018.
|including holidays & travel|
a) our long winter break was used as a proxy for all the 'Holidays & Travel' category, and its costs were multiplied by 2 to represent the other holidays we also take throughout the year. Because our 2018 early break was actually paid for in late 2017, I calculated the costs which would be incurred today of taking an identical trip in early 2019, using exactly the same flights, accommodation & duration etc.