As for the AUX Input...
I have a 2003
Seat Ibiza, with the CD6 button (but without the CD Changer)
Basically once you remove the headunit, purchase this:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=350370717038
It is for a Smart, but works in our Alana headunits.
Plug it in, and earth pin 14, so a small wire touching pin 14, and attach the other end to the metal part on the rear of the headunit.
Once all fitted, feed the wire out from your centre console and plug Iphone in.
Hit CD6 button, will appear 00:00 but when you hit play it will work.
If you get the message "changer" then it flips back to FM or something,you haven't earthed pin 14 correctly.
Il try find the thread with the pinout diagram, if not il grab some photos of mine.
Jack
EDIT:
http://www.seatcupra.net/forums/showthread.php?t=127865&highlight=aux+alana << That has the pinout diagram, pin 14 is in row C column C3...