Basically - when you take the headunit out, there are 3 coloured plugs, GREEN BLUE YELLOW at the top left (If I remember correctly)
The blueandme and USB MP3 player feed into the yellow connector via 3 wires.
I unplugged this yellow plug and disconnected the 3 wires.
I then took my aux lead (headphone wire) and seperated one end of it into LEFT CHANNEL, RIGHT CHANNEL, COMMON.
You then need to solder these new wires into where the previous had come from. LEFT + RIGHT CHANNELS (white and red wires) go in the side holes and the COMMON goes down the middle.
Finished.
-----------------------------------------------------------------
For this to work, you still have a memory stick with MP3 songs plugged in, So the computer thinks its playing the music on the memory stick. But in reality whatever you play down your new aux cable is what will come out of the speakers if that makes sense?
This will prevent you from using the BlueandMe handsfree - but as I have an iPhone all calls will come through the aux cable anyway, just like if I had headphones on.
The sound quality is fantastic! Just like a CD. No interference with engine or mobile phone either. And is easy to remove the aux cable and revert back to blueandme when it comes to resale!
Top stuff!