I'm BA EC Gold and will be travelling with my girlfriend who will be BA Silver by the time we start the trip. We're based in London but Istanbul looks like a good departure point

Being new to the OWE concept, we're a bit confused. Nevertheless, our initial planned itinerary is:

IST-LHR-BKK-HKG-NRT-HKG-PER-ASP-MEL-SYD-AKL-SCL-LIM-EZE-GRU-GIG-LHR-IST

I'm aware that this doesn't use all the available segments for each continent, but time is a bit of an issue. I'd appreciate any advice and have a few questions:

* What is the best-value way to fly LHR/IST initially? Y would be fine.
* Do we have to fly the final LHR-IST segment?
* Would someone mind PMing me the email address for BA Istanbul?
* If I decided to splash out, how well would this itinerary work as an AONE4? It probably has too many flights without F to make this worthwhile, but is there a clever way to re-work it to take advantage of an AONE4?
* Have I missed out anywhere important?!
* Assuming we do the trip in one go, how long would this trip take, allowing for a couple of days in the key locations. This isn't purely a MR - we'd like to enjoy the places we visit and get a taste for future trips!

Thanks very much!