I notice you posted the same question in the BA forum. Are you redeeming Avios? If so, not sure how much us CX folks will be able to help you even if you're trying to fly on CX. For example, with AsiaMiles you could waitlist for the award you want, but I don't think that's an option using Avios. We also won't be experts on issues like change fees for BA awards if you book a back-up now and want to change later.