I went and upgraded to Windows 8- BIG mistake- Can anyone advise how to remove?
Its Windows. Its tightly integrated everywhere.
You're going to waste away hours of your life trying to do an unsupported downgrade. You are obviously not that much technically minded when it comes to computers (otherwise you wouldn't be asking the question here).... therefore you can probably expect to spend days not hours !
Backup your files (just your files, not any software that you should simply be reinstalling). Then format and re-install the prior version you desire.