I have a Audi A6 2004 with a radio/sat nav. I had the battery disconnected, and I have entered the wrong code in, and it is now in safe mode. I have found the correct number now, but it will not let me do anything. Do I have to take it to a dealer ?

I did the same thing in my old B5. You need to drive around for about an hour with the radio on. Eventually, it will reset and you can reenter the correct code.