Chorus Radio Head Unit Removal

I've just been to Halfords to get them to put a cd changer in by attaching it to the existing chorus radio. They had the right removal
keys etc and the right side released fine but the left side didn't release at all, the guy said that it didn't even feel like the catch was there. After about 45 minutes he gave up and said that I should try to contact Audi and see if there's a known fault or any way of releasing the radio from underneath. Has anyone got any idea of how I can get this out or come across this problem before?
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