Check the programs that are on your computer

Windows: Start > Control Panel > Uninstall Programs. Mac: Open the "Applications" folder Linux:

• Ubuntu Unity {web link}
• Xfce: Applications Menu category sections
• options depends on the package manager and the desktop environment

Go thru the list. If you find something that you don't know what it is, use a web search.

Troubleshoot Firefox Issues Caused By Malware {web link}

Also;

Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

already tried that route - one would think Google would be all over this but the dearth of support from them leads my cynical mind to think Googlr has a financial benefit here - fees from Yahoo perhaps??

Thanks for the effort though - i appreciate it

Google searches are automatically redirecting you to a Yahoo search page? Does that redirect happen when you do a search from Google's website directly, or only when you're using the search bar?

I have Google as a homepage & I start almost all my searches in the Main Search Box - sometime in the little one at the top right - never in the url/address box

Sorry to say that just sounds a lot like malware. Have you already asked in those forums? If not try asking in one of the forums specializing in malware removal; forums are provided in the link FredMcD's answer (another one that seems helpful is malwaretips.com). Until you are sure that there is no malware or it is completely removed, you may want to be careful with any passwords you use. Good luck with this.