Welcome to the Bunnings Workshop community @Buster. It's amazing that you've joined us, and many thanks for your question on deck footings.
We'll need a bit more information about your project for our members to offer some helpful advice. The style of footings used are determined by what factors you have to work with. What is this deck being built over? How high from the ground will it be? Does the ground change in elevation? You should find @Adam_W's guide on How to build a low-level deck useful when planning your project.
You might like to start by posting some images of the area and a plan of your proposed deck.
Gal stirrups have been a popular choice for many years when it comes to building decks, and generally, you can't go wrong with them if they are installed correctly. There are other alternatives these days, and with further information, we might be able to offer some other solutions.