There will be 100 times more pints of Guinness sold this week at the Cheltenham Festival than pints of Guinness Zero. But the numbers of Guinness Zero being poured at the four day meeting have steadily been increasing over the years. At least 3,500 pints of Zero will be sold at the world famous festival week - compared to almost 400,000 pints of the full-strength stuff. The Festival starts tomorrow and will attract over 230,000 racegoers. Although the popularity of Guinness Zero is growing fast