BOAC
Thank you for the suggestion, in Chrome /Settings/Manage Search Engines/ one gets a list of search engines and is able to select a default. What you led me to was the ability to then hover over an unwanted one, this shades over and - surprise, surprise, an X appears at the end of the line - hitting this removes that selection !
Unfortunately the laptop that started all this is not available at the moment - I'll try if I can get into that same page on the installed Firefox when I get it back, and wipe out Delta Search - and Bing, and a couple of others that have appeared from nowhere.
Slowly learning !