I fell off twice on Saturday due to ice on the road. I've ordered a pair of studded tyres.
EDIT
Well, I tried to order a pair of studded tyres, no free stock. I've now ordered a
Continental Top Contact Winter which I'll try on the front wheel:
"The Top Contact Winter contains sharp granules in the rubber compound, thus aiding grip in wet and snowy conditions."
EDIT2
Top Contact Winter tyre arrived. The packaging says:
"...the tread also has microspikes made of rough, sharp-edged granules. With these microspikes, the tire can bite into even frozen surfaces."
I'd feel a little happier if they'd used the word 'ice' somewhere.