I did a bit of a search withnthe limited time I have at the mo for you Nelly and only came up with CVP in Lightning Ridge. The town may have a laundromat though but can't seem to locate it for you. Maybe give the local PO a ring or even the local Police if that desperate to do some washing.

Collarenebri is a pretty little place, had lunch there on our way back home last month. Had a quick squiz at the Camps 6 Bk and #899 is Collarenebri Primitive Campground, a camp area at the eastern end of town, next to the football grounds. Max. stay 48 hrs. There does not appear to be any actual caravan parks there.

Hope this helps
Pejay