i buy lots of cheap old cameras and lenses - many of which have some quite bad fungus. Try careful use of a lens wrench/ spanner (try microtools www.micro-tools.com/Merchant2/e_spanner.htm) to get it open then very gentle application of acetone nail polish remover with a lens tissue, allow to dry, repeat until its all gone. give a final VERY delicate clean with a tiny amount of windowlene (also known as windex i think) on a microfibre lens cloth, then put it back together. works for me.. Just be careful not to get any dust in it before you put it back together.