I'm not sure, but they're certainly going to have to do some SERIOUS shagging between now and then to overcome an almost 30:1 ratio!
Even that figure is making an assumption that all the people counted as 'Muslim' in the UK census would vote in favour of the introduction of Sharia law. Which is not the case at all.
Kidding aside, if muslim birthrates exceed native rates by say 2 to 1 (I think natives are at about 1.5 kids per female, with muslims over 3.0), then your 30:1 ratio will be cut in half in a couple of generations, even without immigration.