existing photo in passport

My Aunt had the same problem.


I'm pretty sure it will be, as the majority of your face is still visible, unless you had one of those RAF handlebar jobbies.

In addition to that, I would guess that you have one of the "new" passports with built in bio details, which you can use to go through automated barriers in most Euro airports.
If you are still worried, why not paint on a moustache for your day of travel...