How do you change/check the units used? I have a feeling its defaulted to inches

And what's wrong with inches, may I ask?
Back off Brussles!

mm rule!

Come on don't be scared...
We also lost our el, pond, ons.

In the end it's easier to have the same.
And also the same coin...

Tools dropdown

thenOptions

Document Properties

Then select Units and you will be able to change from imperial to metric