If he does end up flying Qantas, get him to join QFF anyway (it will cost nothing if he uses his UK address).
He should earn about 19500 points for LHR-PER (via SIN) and MEL-LHR
When he gets home, he can order his Mum a $100 gift card for 13500 points (or if he makes it to 20250 points, he can...