A bit confused at what you need.

do you mean you want to get a seperate USA-LHR-USA ticket? or what?

If this is a MR then you are not really doing too well.

I will NEVER take the flight to AKL and then to USA
As you miss out on the SYD-JFK miles and then another Trans Con available
in Europe you are also not doing much as well.

But i guess you need to goto both USA ans EUR then RTW is the only reasonable option.

I think the LHR-USA-LHR segments you just have to pay for another ticket

(also remember the 40 Pounds per intl dep tax on J/F/T class from all UK Airports)