I re-installed a new version of the Admin Products_Insert.php and it does work now.
[EDIT] Image issue resolved as well with the uploading of a fresh doc.
In order to have my new data retained in the new field, do I have to insert a validation behaviour? Neither of these items would be 'required' - one lists the ingredients of a product and the other lists any testimonials that customers have provided.
HTML Editor - thanks. I just downloaded it - haven't figured it out yet.