I have recently come back to try FF again, but I now remember why I stopped using it last time.
The following extension is missing: https://addons.mozilla.org/en-US/firefox/addon/googleuk/
Which means that there is currently NO WAY for me to set my search default to Google UK.
When I search in the omnibox, it always directs me to google.com.
I’ve got UK set as my language and location for the OS and FF.