Unfortunately I have never witnessed it. Given that the London area saw some I was pretty unlucky.
According to this, most notably during the Little Ice Age, October snow in the south was commoner than some might think.
http://www.netweather.tv/index.cgi?action=winter-history;sess=
I hope it becomes more common again, the closest I've come to seeing it was a few minutes of falling snow in late October 2012 that rapidly turned to sleet and then rain. The earliest I have seen settling snow (that I remember at least) just scraped its way into Autumn 2010 on the 30th November, which probably sounds ludicrous to some people. I hate being in the south east sometimes.