I'm pretty certain that the law doesn't accommodate the concept of an indoor and enclosed designated smoking area. It would have to be open to the elements to a certain degree. One way round it is to permit smoking on the spirals going up to levels two and three but then you're going to upset the non-smokers who have to use them and the smokers in level one who don't have access. I'm guessing here but it's possible that Premier League regulations may totally ban smoking within stadiums anyway even if there's a legal loophole that would theoretically allow it.
As has been suggested, it's poor form if a smoker can't do without for a couple of hours. I quit about five years ago and always managed that fine - though long haul flights (remember those) were a total nightmare!