I felt that 20% off Catch was not quite good enough, so after a bit of searching around I found that Unidays offers 10% of Catch. The best thing is that you can stack with your Coles discounts. I confirmed it with a purchase just before I posted this.
You need to be over 16 and have a student email ([email protected]) to sign up. It's as simple as clicking on the link in Unidays which gives you a one time 10% off code. This code gets put in the coupon code section in your shopping basket on Catch, and the gift cards go just below in the gift card section.
T%C: Discount is valid for UNiDAYS verified members and is available online only at https://www.catch.com.au. Excludes all Marketplace, Apple and Nintendo products, and delivery fees. Cannot be used in conjunction with any other offer including referral codes and promo codes. Prices are in AUD.
Make sure that what you want to buy is not a Marketplace item. The Xbox One S I got for $214.60 was fine, but the Sony WH-1000MX3 and Bose QC-35II headphones that I was eyeing off are both Marketplace items making them ineligible for this deal.