Question about x-default for international domains

[YulesB]

Hello!

We run several international websites. Some have the same languages, but different locations. The websites are for the same product but work totally independently - which means their site structure and content is often different and not translated directly (though some of the content is similar).

The problem:

One of these website is for GB with English as a language: hreflang="en-gb"
We have also one global website, which is for users from languages/countries where there is no website available - hreflang="en"

The problem we are having is that the global website (hreflang="en") is ranking higher in GB, which we want to avoid as the local website should rank in GB.

I thought to add the x-default attribute to the global website, hoping that this would help to rank lower on Google UK, but I was wondering if there are other options how to solve the ranking problem?

Also, I was researching but not sure if I understood everything correctly: Do I need to add the x-default attribute to the home page and all other pages where we have ranking problems or to all pages?

Thanks