I took the only sane route and wrote a plugin. I'm told by my colleagues it the single most useful piece of code I've written :-P It clones a layer to memory or shapefile with the choice of copying all data, selected data, or definition only (i.e. including attributes and styles). Been meaning to clean it up submit it the the repo at some stage, but for now it's at https://plugins.lparchaeology.com/qgis/plugins.xml and called ARK Clone. Simply right-click on the layer and the clone option is in the pop-up menu.

John.