I think this is relevant to other languages as well.
It only seems to affect TV Libraries
When you add a New TV library you are given a drop down of languages:
So that means the Library will default to English (United States)
and once you have completed adding the Library then it will start the scan.
So if you want English (United Kingdom) you need to cancel the scan and then edit the Library, at which point you have the option to set the language to English (United Kingdom)
