Appreciate the responses, thanks.
VX has thrown a spanner into the works, the MC non-refundable fares have dropped to $69 and the MCS fares have gone up to $200.
May well buy the MC fares and as the 24 hour mark is just before we leave for SYD airport and as I would probably know of any possible delay by then, see if I can spring for an upgrade. Otherwise, given it's only a 1 hour flight, just grab row 5 (still showing as available) and enjoy the ride.