You should get camera attended to before whatever is growing inside gets worse. Sorry I don't know cost of cleaning. If Camera Workshop doesn't do cleaning, across the road at The Adelphi in the basement is a shop called P & G Photographic Centre (6837-0697), look for David.
I'm not sure abt correct drybox settings but mine's at 30%. Sorry to say but fungus/dust is everywhere and it's very hard to completely eliminate.