I am trying without a lot of luck to get a 241 in first or CW to Sydney.

However i can get a LHR-HKG and a SYD-LHR (i can then purchase a 1 way HKG_SYD)

Can i do that on a 241 or do the routings have to match?

I have done a LHR-LAX and back from Tampa before but as this is 2 different countries will it be a problem.

cheers