Thanks for your suggestions and info Kris, greatly appreciated. Don't I already have the Stock KitKat Dialer on my Google Play Edition Galaxy S4?
Hey @Rob, I'm using the stock KitKat dialer on the Nexus 5 and you can add numbers to the blacklist direct from the dialer with it. I can't recall if it's been added to the Play Store yet (and I have no idea about it's app compatibilities) but you can sideload the APK (the app file) direct onto your S4 GPe because you've got KitKat. The APK and zip file links are in an article I wrote recently: www.androidpit.com/how-to-install-the-kitkat-dialer It might be worth a try. The process may seem a little fiddly (and you require root) but that's Android for you! Enjoy. But let us know if you find a good alternative.