Entry not excerpt
Haha, I just learnt how to use my own blog - the visible section of code which is an introduction to the extended behind-a-link content goes in the "Entry Body" (which I misread as "Entire Body") not the Excerpt section.
Fixed it now. Became obvious when I actually looked at my own site. Now the last four entries have an introduction. The rest of the blog is the same.
And I commented on my own GRUB geek entry, because I discovered I was a bit stupid.