Hi. Just a bit of useful info
Had an A3 2004 8P1 (2.0 tdi) and the battery went flat. The door lock also didn't operate with the key, probably because it never got used due to always using central locking.
The way I got over this was to jack the front of the car up. Remove the shield under the car, Remove the cover from the starter motor and connect the positive clip of a jump lead to the positive lead on the starter motor and the negative to the engine block. I then connected the jump leads to my other cars battery and operated the remote control. This allowed me to open the bonnet and re charge the battery.
You could also do this with a jump start battery pack.
Hopefully this will help someone else out.