What about putting it in the freezer? Mother said thats a good way of getting the smell/taste out of plastic when you've had something smelly in a tupaware container. Never tested this.
Wow, I left this alone for a day and now it's filled with stuff that kinda makes me want to burn the joystick and then burn the ashes just to be safe! Thanks for all the suggestions (at least the ones that won't make me question touching it again ). I shall try all the disinfectant based techniques, followed by Margo's bicarb idea. Failing that, a vinegary smell would be way better than the current one. God, I can smell it now - and I'm sitting about half a metre away. It's definitely not a decaying plastic smell either.
You can smell it from half a metre away?! Ugh, destroy the thing. Honestly; What could make it smell that bad, that you're half a desk away and can pick it up? Actually, no-one answer that one.........
I think if it were me I'd just chuck it in the bin, or in the very least put it in the next charity bag that comes through your door.
Just a small update: I wiped the thing with a bit of kitchen roll dipped in thin bleach (UNDILUTED) which made it smell much better, for a little while at least. It's been banished for a week to a small cupboard with a plate of bicarbonate of soda under it. Now to play the waiting game...
Well, time to put this little saga to rest. Two weeks of the above treatment did nowt for the smell, plus the joystick now failed to work (I forgot to take the batteries out, which may have not helped). It's ended up in the skip. There is a (semi) happy ending though. Someone was selling one that was effectively brand new on the 'Bay and I was the only bidder! This one actually smells like new (this was pretty much the first test I performed) and works...for the most part. Unfortunately the centre tracking is a little off, but increasing the size of the dead zone in games remedies this. At some point in the future I may open her up and have a tinker.
I'm just gonna throw this out there... I'm a pretty clean person. I take my personal hygiene very seriously, and even I am disgusted at the amout of crap that comes out of the seams of my mouse or Xbox 360 controller when I take them apart to clean once every few months (or repair, in the case of the 360 controller). They don't smell though, there's just a buildup of dirt in the seams.
Best thing I've read on here so far xD Co-incidentally I haven't even touched my PS3 controller in months but it's got that horrible slime coating on the sticks, must be something in the air !