I am using Linux Mint, and want to edit my compose keys according to the instructions given here. My keyboard settings are English (UK). However, in the folder /usr/share/X11/locale where I expect to find a en_GB folder, the only english folder I can find is for en_US (which I edited without thinking, and it obviously didn't work).
Where can I find my folder, given that I would expect it to be in here?
Welcome to superuser.
You do not seem to have en_GB locales installed otherwise it should be exactly where you have been expecting it to be. The standard way of doing that is to edit /etc/locale.gen and comment in one or more of the en_GB... locales after which you will have to run (with sudo or as root)
locale-gen
On Debian-like systems such as Mint, you can apparently alternatively also just install locales-all. See this answer on unix.stackexchange.
