I live in the UK. A while ago while working as a copywriter I wrote and proofed about 60+ pages of web content. After chasing the client for sign-off on that stage of the project for a week, they turned around and said the copy was not good enough and that there were a number of spelling and grammatical errors.
I asked them to be more specific, and they pointed out “focussed”, the only error they could find - though, quoting them “I’m sure there were more when I last looked…”
Anyways, focused/focussed can be spelled both ways in the UK. And I’m still out quite a bit of money.