You can get details of the BA/CX award from the Executive Club handbook (joint/partner award travel). You have to download it from the website (access it from your home page via the menu on the top left hand corner).
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Is it correct that I could fly from LA to Australia, then back to Houston through London (with a stopover)for 125K.
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No, all joint travel awards (ie the BA/CX award) are round-trip only, so you can't go back via London unless you go out that way. The routing you are looking for is covered by the OneWorld RTW award, which wasn't in the handbook last time I was looking for it. Maybe someone else can help here as I've not been able to find details of it anywhere. It basically goes by miles traveled...