Which works? Slimming World, Weightwatchers or Rosemary Conley?

I want to lose four stones by Christmas 2007. I have messed about and not stuck to Weightwatchers for the last two years with no results whatsoever. Will Slimming World work for me? What foods would work for packed lunches at work? Has anyone succeeded in losing significant amounts of weight with Slimming World and how long did it take? Sorry for all the questions but I am loathe to go and pay to join and find it is not for me.