If you're looking at European holidays then any changes in exchange rate since Brexit would have affected the price of holidays.
Jan 1st 2019. 1 GBP = 1.11 Euro. By December 2019 it was 1.20. Ergo, the pound had strengthened against the Euro.
July 1st 2024 1 GBP = 1.17 Euro. January 2025 saw it open at 1.20, drop to 1.18 in mid January and it's now back at 1.20 (good for my pension).
The pound hasn't weakened against the Euro.
Aviation fuel cost around $70/bbl in January 2019, it is mid $90s today. The rise is due to the war in Ukraine, mainly. Source
https://www.iata.org/en/publications.../fuel-monitor/
Are there other influences on holiday prices? I'm quite sure our resident bean counters will inform me.