Restrict blocks to specific pages
Sumit Madan was spot on.  Several blocks were hard coded as front page only in the page.tpl in the contributed theme.

For other newbies caught out by hard coding, the cues are:


The visibility settings for a block behave erratically, i.e., in a pattern not consistent with your expectations
When you inspect the regions (/Structure/Blocks - at the top), some of the regions do not appear. Yet, you can put a block into them and the show up when you inspect under Firebug. Now I understand the problem, a quirk that had puzzled me is fully explained.


To find the hard coding in page.tpl, look for ($is_front) and change that to ($page != 0).

page=0 refers to pages like lists of taxonomies. So this edit means the relevant blocks will be available to all pages including the front page and can be managed using the block visibility as usual.

Thanks everyone.