Dont use agents!! Use budget
airlines via their websites. I did asia
last year and took about ten flights over as many weeks. Not one was bought via an agent. I spent hours and hours researching airports, airlines and who flies where and when. I saved a small fortune.
Usually you can go to an airports website and see the schedule. From there you find the budget
carriers. Then move to the carriers site and so on and so forth. From Tahiti you may find Brazil
then Uk is a good option. Even via mexico
if there are connections.
Unless there was super cheap
deals I wouldnt go via NZ or Aus. Its 24hrs to Uk from downunder via at least one to two stops. (Either bankas/singapore/KL then Dubai)