Finally, I now realise that it should be:
[mydomain]\language\overrides\en-GB.override.ini and
[mydomain]\administrator\language\overrides\en-GB.override.ini
This file is obviously not exclusive to JoomShopping, so any language overrides for other components should be added to this file.
However, it should be noted that if you attempt to create a (site) template override from within the Joomla template editor, JoomShopping is shown as a component (com_jshopping) and creates folders for the selected component part, e.g. 'products' under html\com_jshopping, but there are no files in those folders.
Scrabble
