Thanks for your response.
First I should explain that in the last hour, I downloaded Malwarebytes (free) from Softpedia (http://www.softpedia.com/dyn-postdownload.php/4da55095eb250a3742025ebdcf058222/580a4e8d/13ebe/0/1?tsf=0
...and something was found and removed from Firefox. It wasn't named 'Bing' but Bing has now been removed.
I had previously tried changing the defa...