Many thanks for the replies so far.
I have downloaded and installed Universal Media Server but unfortunately I am not technically literate enough to understand how to get it operating (I can barely understand what it does). It shows my iPhone and an "unidentified Renderer" as well as Windows Media Player. (I haven't purchased WD TV Live yet and I don't even know what a "renderer" is). I have not been able to work out what players UMS will work with. (MusicBee doesn't seem to be supported). Windows media player indicates "no media devices found". I really think this is beyond me and I don't expect anyone to spend time trying to educate me so I might abandon UMS unless it appears to anyone that I am missing something simple.
Are you saying that the Airplay plug in will stream from MusicBee to Apple TV? There is not much info on Eric Milles site about how this plug in works. If not MusicBee, what players are needed?