In reply to rob.s22: March is probably a good time to visit. It can still be hot by British standards, so selecting the right crag makes a difference. A lot of the crags face west, so they're fine in the morning, but you'll want to move once the sun hits them on a warm day. Good sheltered/east facing crags are Centennial Glen, Logan Brae, Boronia Point.
The Blue mountains is more of a sport destination as well. There is trad around, but be aware that the rock is softer, so protection is not as bomber. (There was an accident over xmas/new year where a couple visiting from inter-state were not aware of this)
Also, an alternative to the campervan is to just catch the train from Sydney to Blackheath (single is around $A8), and stay in Blackheath climbing at the crags nearby.