Error creating Workspace based on Custom Template

Adding items to a list (announcements, links etc.) on a sub site (workspace) that has been created using a custom template by a user who is not an Administrator, but instead granted the "Create Subsites" returns the following error

"Error - This form is not available for this list, discussion board, survey, or document library.
Troubleshoot issues with Windows SharePoint Services. "

This is because, contrary to Microsoft documentation, merely granting someone the right to create a subsite isn't enough for them to create one based on a Custom Site Template. The user also needs the following additional privileges
- Add and Customize Pages
- Apply Themes and Borders
- Apply Style Sheets

Also refer to a previous post - Can't view Custom Templates in WSS for more workarounds to get custom Site Templates to work.