Thanks for all the replies, guys.
I have gone ahead with the standard pipes (as had no other choice) and then will get my dealer to retrofit G56 pipes after I take delivery of the car from the factory.
G56 currently don't have their stage 1 kit in stock but they have said new stock of the exhausts should be coming "within the fortnight and the air filter cover assemblies within the month". I have put myself down on their waiting list.
High Noon, your Magnaflows look and sound great but I have no mechanical expertise whatsoever so I'll be leaving it to my dealer to install the G56 kit.