Had the first snow fall of the winter season at home this morning and on the run in to work on un-gritted roads I pondered, now would be a great time for winter tyres.I'm in the camp of thinking that drivers in the UK and certainly the South (most years) don't really need the extra expense of winter tyres but there has been some debate on here over the past couple of years.The question is, if legislation changed and we were made to use winter tyres, when would be the right time to fit them to the car?For instance, not so long ago (14th November), I was on a track day at Brands Hatch in the warm sun shine, cooking my "summer" road tyres in the process. The wrong time then (on normal roads) to want to think about running winter rubber. Now a matter of weeks later, we are driving in snow.So when do you change? How do you legislate in this country when you should and shouldn't change tyres?It's all very well saying when the temperature drops below a certain level but where in the country would that be and how long for? If we had a cold snap, can you imagine the rush at the tyre shops and the back log?What's your thoughts?