Hi Michael,
Very many thanks for your speedy and informative reply. I'm not actually sure what much of your reply means,and I'm confused as to why the modal window works pretty much as before in the admin, but not on the front end? For now, I've now switched to the Javascript confirm option (which is not ideal) because the Modal window option only displays the dialogue box below the footer where it's difficult to see. I look forward to your new version when available.
Best,
--Gary.