We stayed at Richmond in late 2012. Wanderest Travellers Park. #453 in CAW 6. You can stay three nights for 'free', but you have to join the Richmond Club to use it. Richmond Club owns the area and is just across the road. It's on bitumen, but there's power, toilets and showers, and good meals at the club. Apparently it's a good base to get the train and see the sights of Sydney. I was sick at the time, so went nowhere.

Woops! re-read your post and realised my suggestion wouldn't be much help if you're staying 3 weeks. sorry about that. Someone else may have a better suggestion.

I hope you enjoy your stay.

-- Edited by Beth54 on Saturday 10th of May 2014 04:20:20 PM

#453.is a location number for the camp site in NSW and CAW 6 is the name of a book. It is the nomads bible when it comes to travel in this amazing country.
CAW stands for CAMPS AUSTRALIA WIDE and #6 is the edition. The book is available from Newsagencies and some bookshops. CAW 7 is now on sale
and has upgrades so if you are going to buy the book make sure the upgrades don't change the location as it often does. When you pick up your camper ask the people if they have a copy they can lend you. The book is quite expensive.
Hope my explanation helps.

Mongrel.

Gday...

Bitta info re Wanderest Richmond -

http://www.wanderest.com.au/page/MTg3Mw/Stay.html

Cheers - John

Wanderest is on the railway line into the city so easy to get in and out. About an hour I think.

Our favourite caravan park for Sydney is Lane Cove. It is surrounded by the National park, is a good, quiet park and has a bus stop out the front. We caught the bus, got of and caught the train for the rest of the way into Sydney.
www.lanecoverivertouristpark.com/

Another good one, but further out, is the Parklea garden village is located 35mins from Sydney centre. The park was very clean and tidy with good security. There are 2 swimming pools and a separate Spa. Nice BBQ's and picnic areas, Recreation room with T.V. Located just outside the park, is the Bus stop, very handy. We caught the Bus to Blacktown, then the Train direct into Sydney, this was very easy to do. We thoroughly enjoyed our stay at this park, and would recommend it and stay here again.

As with most things in Sydney, caravan parks aren't the cheapest either.

Aus-Kiwi's suggestion is the best option in my opinion. There is a train station in walking disgrace from the CP (which is lovely) and it is much closer to the City. I haven't tried the Richmond suggestion but you will be on the train for over an hour perhaps even an hour and a half each way. Not much fun. You could spend that time enjoying the harbour.

Many years ago we had the same idea. e stayed in Katoomba in the Blue Mountains and took an early morning train ride into Sydney, That train ride was the highlight of the day! The scenery was absolutely wonderful going through the mountains. Yes it was a long trip, but well worth it.

As I say, that was a very long time ago, but it's possibly still an option for you. The other bonus is that Katoomba is also worth visiting with lots of things to do and places to visit.