Consider a Oneworld business class round-the-world (RTW) ticket with travel beginning and ending in Norway. The base price for a 4-continent Oneworld Explorer ex-OSL Is around 1800 quid cheaper than the same ticket ex-UK, and has a price that can often be considerably lower than a conventional return ticket.

You have to cross both the Atlantic and Pacific oceans in the same direction and end in the same country where you start. It's good for up to 16 flights and has a year lifespan. You'd get 4 flights within each continent touched (6 in North America) so you could include Africa or Asia along with Australia/NZ and North America.

Lots of details on the Oneworld board.

The Oneworld Explorer User Guide