I think I have worked it out.

I was using a Custom Template.

If you open a xara default Template and then the Text tool, before adding any text, check the Document language. Mine has UK so assume this is picked up from the locale settings.
when I created my custom one, W10 must have switched Language Preferences to ENG US, without my noticing. It does this on occasion as I am sure some errant program is badly designed (not Xara).

Anyhow, I opened my custom Template, aded a text area and ensures the selected language and default language were both English (UK) and then deleted the text area. Finally, saving off the Template.
All good not in use.

Acorn