As above really.

Looking for some decent riding that I can fit into a day, or a few hours. I also need to be able to rent a decent-ish bike while I’m there. Any recommendations please?

We went for several walks on Kuringai chase when we were there, and met a fair few riders – it seemed pretty popular, and looked a good place to ride.

They recommended goggles because of the spiders..

Riding-wise:

Manly Dam
Oxford Falls
Red Hill

Bike Hire:
http://bikefactory.com.au/services-page-3/
These guys were great when I was out there. One of them showed me around some of the local stuff to help get me started.

I never got to ride in NSW but when I was out there for a while last year found this site really useful for choosing places to go:

http://www.trailmate.com.au/home/nsw

Thanks guys.