1. first thing to check:
settings -> language settings -> Administrative language setting -> welcome screen and new user accounts -> copy settings.
make sure non of the settings is set to the undesired language.
thanks it's 42
2. another reason why display languages keep adding themselves to keyboard layout lists:
1) press winkey+R
lpksetup and press enter
3) choose "uninstall display languages"
4) choose the language you want to remove and click "next"
5) restart your computer
answer taken from this thread
3. When the two solutions above don't help
open registry editor (WinKey + r -> regedit), edit
Computer\HKEY_CURRENT_USER\Control Panel\International\User Profile\ to list desired keyboard layouts and restart computer.
4. This is a really dangerous option, use it only as last resort
C:\Windows, look for a folder named as the layout you want to remove (en-GB in my case) and remove it / change it's name.
restart your computer