Thanks for all the help.
I now have a editor macro which corrects all the KF8 font issues in a split second.
And I have completely cracked the Goto Beginning issue, after much searching and reading and experimentation. Pretty much everything I found on the internet was partly right, but none entirely right. To make the same source work perfectly for both mobi7 and KF8, with the TOC in the same xhtml file, and to work exactly the same on the Previewer and a real KF8 Kindle, was not easy.
Now that I have solved it, and can see no sign that anyone else has managed it, I am happy to share the solution if you tell me the best place to do so. I can't immediately see the Workshop forum you mention?