This post applies to anyone with an Alfa 159 manufactured in 2006 and that would like an aux in for there MP3 player or phone. I've just fitted this to my standard HU and it works a treat:
1. Item linked above
2. An extension cable
3. A Drexel or an ability to remove a wire from an audio connector (I don't have this ability hence the Drexel)
4. Some garden wire to help pull the wire through to where you want it
5. A bright torch
6. Insulating tape
7. Cable ties
8. Radio removal pins (can be bought off Amazon for 99p)
1. Remove radio using pins
2. Rest radio against gear stick (I didn't disconnected the battery, I left the power cable connected)
3. Remove the top left cable group of connectors, includes a blue and yellow connector.
4. Detach the yellow connector and extract the brown wire (this is where the Dremel came in handy).
5. Insert the brown wire into the new connector (the Celsus cable) and reattach this to the group and insert back into HU.
6. Test that it works; this is where the extension is first used
7. Assuming it works you'll need to lift the gear stick cover (other posts cover this) and shine the light so you can see it to thread through some garden wire.
8. Use the garden wire to pull through the extension cable
9. Use the tape and cable ties to insulate the wiring and make sure the extension won't separate if pulled to hard.
10. Thread the wire through a safe area around the gear stick and reattach the cover
11. Reset the HU back in its cradle and jobs a good'un
To test press the CD button twice, it should say Aux. Bear in mind that you'll need to turn your attached devices volume to max
Hopefully this will be helpful to someone. Good luck.