But CX cancelled his flight. There was no flight to make. A refund is definitely owed, but the trickier part may be restoring the return segment (there's no reason for them not to do it though unless they're just being jerks -- again, they cancelled the flight), and them potentially calculating the refund as the round-trip fare paid less the one-way fare, which might even be negative! But certainly OP should be entitled to cancel/refund the entire CX itinerary if he so chooses, and then just buy a new ticket back from SYD to PVG.