I will try to give all the details of my problem concisely.
My book (including photos) was written in Word 2000.
I did not use Underlining in any part of my writing.
I saved as Web Page (filtered is not an option).
I Compressed and Zipped, uploaded and clicked 'Save as Draught'.
The 'simple' Preview was not good.
I downloaded the Enhanced Previewer.
Brilliant - it opened my Kindle app and there was my book ...
... with underlining in inappropriate places - there is no underlining in the original Word file.
Most of my chapter headings were underlined. And the text of a whole chapter and half of another was similarly underlined.
I went back to the original file and highlighted the offending bits. I clicked Underline twice hopefully to kick Word into touch.
I uploaded the edited text and the Preview still shows the same underlining.