Thanks for all the advice everyone. None of it seemed to work though as all I could do was force quit safari. But then starting safari holding down shift just brought back all the rubbish windows which then blocked me from using any safari prefs or other tools etc.
BUT then, suddenly I was able to clear history & did so double quick and hey presto, Everything is now back to normal. But the thing is don't know exactly why.
But I'm sure I wouldn't have achieved normality without using your advice to grope around. It was exactly that - a grope around which did work without telling me why.
By the way, can anyone tell me how to turn off this horrible predictive text in El Capitain ? I hate it.