I have found that the key to getting the dough really stretchy is the autolyse part: first mix ~⅔ of the flour/yeast with all of the water to make something like a pancake batter, stir for a few minutes, and let that sit for at least 20 minutes. Then add in the rest of the flour, knead, and let rest overnight.
This isn't mentioned in the linked BBC article, but both http://www.varasanos.com/PizzaRecipe.htm and http://www.perfekte-pizza.de/ swear by it, and I think it has made a noticeable difference to my dough.