How long will it take me to get to lose 2 stone?

That depends on rate. Of loss. A good goal is 0.45 to 0.9 kg per week. Eat healthfully ; be physically active. Aim for 7.5 to 8 hrs of sleep / night. Hydrate w at least 64 oz of water / day. Calories burned must > calories consumed. Do both cardio ; weight training.