Sydney

[sepata]

Bit more than 30 mins but there's a great holiday parks in Narrabeen, on the lagoon. You could stay at the hotel in Sydney Olympic Park. Parramatta is 30 minutesish from the city, but very busy and not particularly special - though I might just have that opinion cos I work there :P

[wysiwyg]

When we go to Sydney we always stay in the city itself - in the YHA on the Rocks most often - is then easy to get about, easy to get ferry to Manly, easy to get bus to Bondi etc. - if you want to see Sydney I think staying in the CBD is easiest - but all depends what you want to see. Sydney I find far more difficult to get around than Melbourne - the harbor is so beautiful - but it does make getting from place to place more complicated - but the ferries are a nice adventure.

[Phteven]

Lane cove national park caravan park?

AKA Lane Cove River Tourist Park

ETA - Sorry I thought you were looking for a caravan park. I didn't read properly.
The Uniting Church has some cabin stye accomodation. Try googling Uniting Venues.