I live in the UK and it's really annoying that the Google results are always American. How can I configure Firefox to use google.co.uk instead of google.com?
Go to this page and find Google UK from the list. Click on that link to install google.co.uk and confirm the addition. The new engine will appear in the search bar shortly. Select it from the search bar and you're done.
You can also check this Mozilla Help Page for alternative solutions.
You can also set the default search engine used when you type a search query in the address bar.
Enter the address "about:config", (If it's the first time you've used this, you'll be warned that you can break things here)
Enter "keyword.url" in the "filter" box. Double-click the result "keyword.URL", change the search provider query string and press OK, eg: http://google.co.uk/search?q=
I've not found a way to change the firefox default home page google search, which still annoys me (I'd just change the home page, except now that is the only way to access the restore session button).