I had mould growing on Marge's steering wheel a while back (leather
version, presumably as Martin's). In desperation I gave it a wipe over
with a very bleach-soaked rag, then a wash off with detergent
(washing-up liquid in water). I thought I'd had done for it, but to my
surprise it came up quite well. A lot of surface crud was loosened by
the bleach and it killed the mould really well.

It's threatening mould again (getting excessively sticky in wet
weather), so I may give it another treatment. Very much caveat emptor
(or whatever) though - if you ruin the finish don't blame me, as Marge
is 19 years old and a bit wobegone and I'd nothing to lose as a result.

Regards,

Simonm.