I have been following your instructions. The child select list no longer get's its values from the child recordset. I have also removed the Populate List from Array that was applied to a <tr>.
I have set the rest up following the instructions and the grandchild list now comes up with a long list of blanks (instead of vets names). I have checked and the database does have relevant data - any reason why it would come up with blanks?
Your comment about Foreign Keys also puzzled me. I am using PHPMyAdmin and have never set up Foreign Keys on any of my tables and yet my first Parent - Child Dynamic Drop Downs worked fine. Are Foreign Keys something I should be setting up manually in my database for these drop downs to work?