Several responses found (eg stackoverflow), this method tried and tested.
Open project, right click & copy.
On main menu, Edit, Paste and give new name when prompted.
Edit manifest, change package name(s) to new name(s) in all references in manifest. Save and say yes to update launch config.
Refactor & rename package(s) to same new name(s) (with Update References checked).
Additionally, if a package name appears in an xml file (eg a layout) you need to edit & rename it and if you want your new app to have a separate identity then you’ll probably want to rename app_name in strings.xml and modify the icon.