Thanks for the tips Hitch and Notjohn. I've managed to get my book published at Smashwords, however there is trouble with the cover image and they require me to modify (recify) the situation but I'm not sure what is required.
The first cover image I uploaded (and coded into Sigil) was too small so I created another one and used the recommended dimensions on Smashwords site which is 1600 x 2400. I revised the book and re-uploaded the file.
Now I'm getting this notice:
"Please make sure the cover image is the first item in your EPUB and that it is sized correctly. Currently, if you take a look at it in Adode Digital Editions, you will see that much of the cover is cropped. Many eReaders base their software upon Adobe, so your cover will appear poorly on some of them."
And it's very true... in Adobe Digital Editions there is only about the top quarter of the cover image showing. And yet it seems to resize nicely when I preview the book in iBook reader.
Is there some coding I'm missing where it might pertain to image size? I'm not using a style sheet because the cover is the only image in the book and every chapter is written in its own html file.
Does anyone know the magic formula to make the image behave across all platforms?
Thanks again for your time and help with this.