Sorry for the late reply - my server (GMX) blocked them as Spam yesterday and I have just rec'd the report.
Thanks guys.
I logged in as "humf" to 00, started a thread, and got more or less the same replies. I resized the windows to fit my 17" screen equally, and found , contrary to the posters you referred to, that by selecting in OO Writer -> View -> "web layout" rather than "print layout" both texts remained in place and could therefore be edited simultaneously. I find that this workaround is adequate for my needs.