Here's the HTML code for `starwarssix.co.uk`, with the requested changes:
1. The main domain displayed on the page has been changed to "STARWARSSIX.CO.UK".
2. The link in the navbar for the main logo has been updated to `https://www.starwarssix.co.uk/`.
3. `starwars9.co.uk` has been added to the "Other Related Domains Also Available" section.
```html
starwarssix.co.uk is for sale