Thanks Alan.
For anybody using Siteground (who have a fine reputation, this isn’t meant as a dig against them) it appears that they make the root directory unwritable on WordPress installations.
If you see a message “Jomres dir is not writable” when you try to activate* Jomres then log in via ftp and in the public_html directory create a sub-directory called “jomres” and that should resolve the issue.
* Jomres is actually two parts, for the purpose of working with WordPress. The first part is the bridging code that allow Jomres and WordPress to talk to each other. When you install Jomres thru the WP online plugin installer what you’re actually doing is downloading the bridging code. The main part of Jomres is only downloaded, unzipped and installed when you actually Activate it.