Unless you actually want to spend time in Bangkok visiting airline offices, I wouldn't deal direct with CX. I would recommend doing what I did earlier in the year. I held and priced flights with AA ( though any OW carrier would do ) and then had it taken over and ticketed by the travel agency "Circle of Aisa" in Bangkok who then sent the tickets to me via DHL. There was no need to spend a day in Bangkok; just flew the BA flight MEL-BKK on 1 ticket and continued on to London on on the same flight with the OWE ticket

Dave