There is a King power shop around carousel 13. Not sure if the prices are duty free. If not there are shops either side of the immigration entrance, alcohol/cigarettes and perfume.
I was there for five months so unsure on that. Wasted a lot of time applying to the wrong places. (UK and Canberra) finally when I got the right place it went fast. Wish you good luck Damian.
I am a UK resident, I tried to get a COE out of country. Residency is misleading. It actually is the country you are in that you need to apply from. I was in New Caledonia and as it is a French Colony I had to apply through Paris. Hope this helps.
After deleting far too many responses to your uplifting message, I settled on, ‘if you don’t have anything nice to say, don’t say anything’ have a great evening