It’s official: Australian Music’s night of nights, the ARIAs, is off to a Roaring start. Everyone from Katy Perry to Harry Styles (we’ll just give you a second to inhale, exhale) brought their sartorial A game to The Star in Sydney, setting the hearts of a thousand tween fans – not to mention the Twitter sphere – alight. Before you park yourself on the couch to watch the ceremony unfold – go on, you deserve it! – here’s the only thing you need to read to get up to speed on the #fashuns…