My timetable shows no flight ZQN-SYD, it is ZQN-CHC-SYD (this would force you to pay for an extra sector on the OWE, which is not economical). Perhaps the schedule has changed for your travel dates. Also CPT-LHR in D is sold out for many dates, you might be forced to route JNB-LHR which has much more availability. Once again depends on your dates (and you give no hint of the season). Personally I think your OWE could be improved in lots of ways, but to each their own (you've had lots of suggestions that you have chosen not to incorporate).