I've solved it. To help anyone else doing this retrofit the complete coding is as follows:
09 - Central Electrics
▪ Byte 16, bit 1 from 0 to 1
▪ Byte 28, bit 6 from 0 to 1
▪ Byte 35, bit 7 from 0 to 1
▪ Byte 37, bit 5 from 0 to 1
▪ Byte 37, bit 6 from 1 to 0
▪ Byte 37, bit 7 from 0 to 1
▪ Byte 38, bit 0 from 0 to 1
▪ Byte 38, bit 1 from 1 to 0
44 - Steering Assist
▪ Byte 01, bit 3 from 0 to 1 (this was the part that I missed)
▪ Byte 01, bit 7 from 0 to 1
17 - Instruments
▪ Byte 05, bit 4 from 0 to 1
I also changed an adaptation value in 19 - CAN Gateway for PLA Installed from NOT CODED to CODED.
The coding for this is a bit confusing as PLA is not the same as Parallel Parking Assist which requires a separate module (10) on cars such as the A3. When this is checked in 44, 17 or 09 , an open circuit error code is logged as the car is looking for module 10. Hope this helps anyone else doing this retrofit on the B9 platform.
Oh and thank you both @downtime and @darkchina811 for taking an interest and giving your input. Appreciate your help.