Office Apps Language Proofing Settings - permanent changes

I have been having a lot of issues permanently setting the proofing language to English (UK) across all the Office apps (365).

Changing this setting via "Review >> Language >> Set proofing language" or "Options >> Language >> Choose Editing Languages" has had no effect. 

This is causing productivity issues and I have not come across any good solutions in any other forum threads. 

Please help!

Thanks

P