Depends a bit on how far down Pershore road you want to go. As you say, you will need the "central birmingham " one, and "birmingham south" , and to go all the way down to moseley you will need the "moseley" one. The Bournbrook one will take you down to second avenue, and a little past it, but if you want the rest of Pershore road, you will have to get the "Selly oak & bournville",, "lifford & Bournville" and "Kings norton" I guess you might not be interested in the far end of Pershore road though, but have included all eventualities
Mikw