Hello All,
Just a quick update that the car has been back to the dealer and after contacting Audi Technical, it has hopefully been fixed by replacing the fuel rail pressure sensor and repairing the wiring harness. This is a problem known by Audi through TPI and it has also occurred on VW Tiguan's too.
If you come across this problem, leave the car with the dealer until a ticket to Audi Technical is issued so that the diagnosis can be completed properly.