there were times back in blighty where my hands were so cold (wet and icey gloves) that i couldnt turn the key in the door and I had to wait outside with hands under arm pits doing the jig until the blood came back - and when the blood starts flowing again its enough to reduce a grown man to a crying baby!!
Having said that, like my Dad always used to say, better to be too hot than too cold!
If you are skinny and have hills on your ride which can chill, a wool t-shirt and a mesh back vest helps keep the chest warm.
You don’t need to spend $$ as our winter is short, an old rugby jersey has worked well for me for a long, long time.
Try used bread bags held in with rubber bands as over shoes to keep toes cosy.
The main thing in Sydney is windproofing. It's not that cold down in the basin. That, for me means thinish long gloves, shoe covers, leg covers, arm covers and a windproof gilette or race jersey. Once I'm out I tend to warm up quick. In Europe I tend to have much the same except thicker gloves and more layers underneath. Even in -10 I've never really resorted to anything under my helmet but maybe that's because it's probably all just vacuum.
(ps I do have gloves for the ride in that shot, but I used a self time and I only had 20 seconds to jump back on the bike. It takes more than 20 seconds to put on thick gloves)
What about checking Sydney Cyclist and doing your email before you leave for work, gives you that bit of extra time for the weather warm up. eg yesterday 10C at 7:30, 15C at 9am. Means you don't need any extra clothes except long sleeves and long pants, except for the depths of winter when a jacket might also be useful. Whether the later timing works for you depends on how flexible your boss is...
Christchurch annual rainfall = 648mm, days with rain = 85
Auckland annual rainfall = 1240mm, days with rain = 137
Wellington annual rainfall = 1270mm, days with rain = 159
Sydney annual rainfall = 1217mm, days with rain = 127
On balance I'd say you're just as likely to get wet in Sydney as you are in the North Island of NZ, and stay drier in the South Island. Temperature is a bit more tricky as you need to compare the monthly averages, although I'd put money on Sydney winning.
But yes, Ground Effect make good gear. I have one of their jackets and there is nothing like riding in a jacket that was designed for riding in. Clever things like thumb loops to stop the sleeves from riding up, long at the back to cover your lower back, and cut so you can put your arms on your bars without it pulling tight across your shoulders.