Thanks for the advice guys, I mapped out two routes and gave them a bit of a tonking.
Both start with a few repeats of Kariong Hill, a nice short climb to get the blood flowing. I hit this not long after 5am to avoid as much traffic as possible…
The first route (https://www.strava.com/routes/3804689) took in the climb out of Terrigal past the skillion, and around the back of Avoca. It finished with a few repeats of Kincumber Mountain Reserve. That one had a couple of quite nasty sections i.e. circa 22%…
The second one (https://www.strava.com/routes/3834790) wound through Wattle Tree Road/The Ridgeway/Tumbi Rd - again, beautiful roads with some steeep pinches! This one took in Dog Trap Road, an awesomely quiet and scenic climb.
All in all, there’s a multitude of options up there with no shortage of length/elevation/scenery.
10/10, would ride again.
P.S. the weather was rubbish!