I'm in the same situation only with a 2010 A4.  I had a voltage spike take out the Comfort Module Section 46 of the vehicle software.  Its the one in the boot / trunk.  You can copy and paste the coding in however the VIN from the donor carcis write-protected.  So far I've not found a way around this.  As I'm getting the fault code message implausible signal which Audi told me is there because of the write-protection it has to go into Audi for this.  I'm struggling with getting the car started or at least getting the shift lock to release.  I'll hopefully sort the EPB with the scanner.  I'll update you on the resolve.  The A5 is almost identical save for a different part number on the module.  Hopefully a forum user will know if there's a way like with Toyota to jumper wire pins in the OBD Connector to override this to start the car for now.