this is why I love Flyertalk!
thanks to the help and guidance from someone on here, I have booked it: OSL - LHR - HKG - SYD and SYD - LHR - OSL all in First using GUF (the wrong GUF at the moment but hoping to get that changed) to upgrade from J (all at a great I sale price). ^
Despite the HKG - SYD leg being on CX. The rules have fairly recently changed on this and not all agents (including clearly the one I spoke to on Friday) may be aware of this.
Happy to share what I know if someone else is looking at the same thing.
Separately, I have found a TA in London who has been very good and helpful with this. Again, happy to share details.