Hi Steve,
I don't know of anyone on here having the info you require.
Some of the on-line codes work, some don't - you take your chance.
Is the Concert originally from your car?
If it is, Audi dealers generally will provide the code if you take the car in to them with the headunit fitted, but it must be the original from factory, and this is usually done F.O.C.
If not, Audi will not be able to assist.
Cheers
Jeff