I don't know if any of the Audi concerts can be uncoded off the serial number,I've heard they can't....
Given that you are in Swansea, put the stereo in your dash and take it to Sinclair (Swansea) Audi and say *ahem* that you've lost your handbook and the battery went flat., so needing the radio code......
Sinclairs do not charge for radio de-coding, they told me that a few months ago when they retrieved the code for me (for free) on the Concert in my recently-acquired A4.
Many dealerships try and relieve you of £20 plus to do this job (which is what Cardiff Audi wanted /ubbthreads/images/graemlins/frown.gif)), so its worth trying Sinclairs.....
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