Hey Rabbit Stew,
If you're after a long hill climb in a rainforest, why don't you try the Duck Creek Rd SE of Beaudesert. I've not ridden it myself, but believe it's about 18km of steady upward grade with awesome views which takes you up the back of O'Reilly's. Then you get to ride it down.
Some of the guys on this forum (?Munrubenmuz, MTBDerek, Zadam etc) seem to be organising some interesting Forestry Firetrail rides in the Border Ranges lately which are also hilly and in the Rainforest.
As for Mt Warning, the good folk on here have already pointed out that it's off-limits to bicycles. Shame.