Hi To replace the UK button go to options at the far Right of the Goggle bar click on it then click buttons.
If the UK button isn’t ticked tick it and then click Add.
If it is ticked UN-tick then re-tick and click Add.
Close all windows on the red X and re-open Firefox page.
You should now have the UK button added to Goggle toolbar.
Thats how I have just got mine back.