Check your passport and travel documents before you travel
There are appears to be a little known issue with UK Passport validity in some European countries.
Since 2020 the European Union decided that the UK Passport needs to have at least 3 months remaining on the expiry period and most importantly it has to be within 10 years of issue.
Whereas previously, you could travel throughout Europe with a passport that had at least 3 months until the expiry date, now it seems that it has to have 3 months left from the 10 years from issue date.
Now this is the important part that may not allow you entry onto a plane or ferry and it is because previously the Passport Agency allocated 10 years on top of any remaining time, so this was added to the expiry date if you renewed before it ran out and you could have a passport that has 10 years and 6 months on it.
SO IN A NUTSHELL .... Ensure your passport still has at least 3 months left from the 10 years from the 'Issue Date' and not relying on the 3 months from the expiry date!
Check with your travel provider to make sure your passport and other travel documents meet their requirements.
Other articles of interest about travelling in Europe with a British Passport following changes in Brexit rules
https://cheapholidayexpert.com/blog/is-your-passport-in-date-please-check-it-now/
and another one:
https://www.theguardian.com/money/2022/jan/29/uk-travellers-could-the-new-brexit-rules-catch-you-out