How long is a piece of string? It depends on a lot of things including what your diet is like before you start, how strictly you follow the plan and whether you exercise. But at a couple of pound a week you could be heading for your stone award.
And tips? Just follow the plan as SW say you should, weigh and measure everything you should be, no tweaks, have your syns, eats lots of superfree, get lots of variety and drink lots of water.