We have been booking RTW from Oslo because the prices are good and Oslo is a lovely airport. Also Qatar flies from there (eg OSL-DOH-SYD or OSL-DOH-ICN) which gives you some excellent product to choose from. OSL-HEL is also a quick hop with some good Finnair flights from there (eg Japan).

If you get to Oslo the night before it’s super easy to get into town on the train, and there are some fabulous museums - notably the new National Museum (we only got to room 22 because there is so much to see and will start from 23 on our next RTW :-) ) and the new Munch museum.