Hi. It's okay, I've just discovered the easy solution.

Microsoft Office Button > Word Options > Advanced > Font Substitution
Word 2007 was 'misrecognising' the the TTF 'Times Norman' by its original older name 'Normyn' (1997) and was trying to substitute another font which did not have any symbols assigned to the relevant character codes.
It was one easy step to select 'Times Norman' as the substitution font and mirabile dictu: the document looks just how it should, again.
Thought there must be some sensible, simple answer. . . Relief.
Peace to all!