OMK3 makes my point; this should have been automatic. Now I know it, it's not an issue, but it seems to me that 'collections by tags' should perhaps be different from 'collections by author' and that the 'collections by author' which I now achieve by tagging the author's surname (not 'surname, forename' else it appears in two lists) ought to be the default display on the 'books by author' list.
I'm still looking at options as to how I should separate 'E. E. 'Doc' Smith' from 'Sadie Smith' - as above, 'Smith, Doc' doesn't do it...
I think though that I shall post a feature request for Calibre, automatically to fill the name sort and tags fields when the author's name is filled.
Apropos of which - I discovered that clicking on the Reader icon when the PRS300 is attached allows me to edit the contents of the reader directly - a lot faster and simpler than ploughing through the menus to get to the 'delete' on the device itself. I'm doing a lot of that at the moment as I play with formats and chop and change!