If you do not use the Tag checkbox in your normal workflow then you can try the following :
- Use the Find utility for All images, looking for Glasgow.
- Use the Find utility on the Selected images, looking for Port.
- Tag the Port Find results with the Command + shortcut or the Image menu option, Tag photos
- Use the unTagged option in the View menu to hide the images with Port Glasgow.
- Use the Find utility one more time for All images, Looking for Glasgow.
Once you have updated just the Glasgow images, change the View back to All. The Command-t shortcut will select the Tagged images and the Command - shortcut will unTag these images.
Best regards,
--Bob