Have just (had to - thank you MythTv!) reinstall Mint13 Xfce.
Thought this would be a good time to try AptOnCD taken from a corresponding install on another machine. This seemed to go ok although one still has to perform various configurations but all the additional apps seem to have made the journey!
However, on opening Synaptic, 10 broken packages are reported all of which are LibreOffice components plus python-uno. The problem and error seems to be down to libreoffice-core which is at a different version to all the other compents.
Whilst all the other components are at version 220.127.116.11-Oubuntu4 upgradeable to 18.104.22.168-Oubuntu5, libreoffice-core remains stubbornly at 22.214.171.124-2ubuntu1. The original is at 126.96.36.199-Oubuntu4.
Fix broken dependencies fails. Upgrade all largely fails because of it, and trying to upgrade it individually fails - all with same error.
What went wrong and how can I get out of this viscious circle?