I am planning a herbacious border in my newly inherited garden in Oberon and would like to try companion planting. Plants will need to be wind hardy which narrows down my range! but would love to be able to companion plant.
I guess you mean companion in the way of looks - but we'd need to know what else you have planted to make suggestions.
Alternatively you can companion plant for pest protection.
Miniature basil - not the tall gangly ones, you can get mini basils that look great and make a good contrast with most other low growing border plants like Lobelia, Alyssum, Portulaca, Marigolds etc.
BUT THE BIG THING IS - that bugs don't like them because they are so malodorous (smelly).
Lots of basil in your garden will help keep it bug free - and it makes a great smell for humans to enjoy too. You can also harvest it to make wonderful pesto too.
Here's a link to the Herb Seeds section of the Garden Shop:-
https://www.gardensonline.com.au/Shopping/GardenShop/Category_35.aspx