I'd try to get a second hand road triple chainset and matching BB on e-bay, for <$50. I'd keep your existing FD and shifter, as they'd work adequately (you'd need to lift the FD a little up your seat tube).
Given the small improvement in gearing, and the value of your bike, spending any more simply isn't worth it.
You may also need to work on getting your cadence higher - 48/11 should be adequate for all but relatively steep downhills in Sydney.