Thanks to all for suggestions;
We got it sorted!
We opened each .lyx file in wordpad and conducted a find and replace from within this.
After experimentation we found that Lyx marks up quotation marks as one of the following dependent on type:
Quote eld Quote erd Quote els Quote ers Quote sld Quote srd Quote sls Quote srs
And these strings are what you need to search for using the text editor.
Rob S
