Pints, you mentioned an mp3 player, and no one has mentioned it since. That seems a bit daft, how do you hear traffic coming from behind you? 
Use your eyes as well as your ears.
Dont wave in and out onto the middle of the road.
Motorists normally dont try to knock cyclists down, so you shouldnt have to worry.
Dont play the ipod at full blast - you should be able to hear both traffic and music.