Outlook Email Default Dictionary

[Peter]

I use Outlook and MS Word as my email programme.

I cannot change the default language from English US to
English UK or International. I have used Tools, Language,
Default and so on, and looked in all sorts of places, but
every time I start a new message, the default language is
always Enlish U.S.

How can I persuade it to start in English UK?

Many thanks

Peter