Getting a head unit with cd changer working

[dneedy]

What I am trying to get

• CD changer connector working (So that I can plug in a grom unit)
  
• Retain the steering wheel controls
  
• Head unit must fit into single slot (not a double height unit)
  

What I have

• I have a chorus tape unit (car made in 2000) - Pinout is http://www.tehnomagazin.com/Auto-radio-car-connector/Audi-Car-Radio-Wiring-Connector.htm
  
• I connected the aux unit to the cd changer connector, then realised that the CC/CD button just switches the head unit to tape mode
  

So, is there

• a) A way of making the CC/CD button trigger the cd changer (unlikely i guess)
  
• B) Does someone know which audi cd head unit is pin compatible, and meets what I am trying to get