Thanks to Kovid and MSWallack in particular finally got it working the way it should. Not totally computer literate but persistent and I do get there. Instead of having a rant (unlike some posts) and saying its no good and not listening to the guys you are asking for advice I just try things and eventually the penny drops.
In my case, if its any help, in Preferences under Email Sharing I took my BT Mail Settings and entered them in the boxes at the bottom. Googled for the correct Outgoing Port settings and Host name . Ticked SSL
Sent book using *****@kindle.com (as set up under Amazon)
Worked fine. No need for a Dropbox workaround.