Because I'm now struggling to lose the last 1-1.5 stone I want to. I've stepped up my cardio and my cals are lower and I wanted some extra help.
I'm not slamming supplements here (before you assume I am) - I use a protein supplement myself - however, if your weight loss has slowed, increasing cardio and cutting food intake further (thereby increasing your calorie deficit) is not the answer. The answer is to reduce your calorie deficit by eating more.
Bodies are funny things. They respond best when you're subtle and "trick" them into doing what you want. Create a big calorie deficit and you'll trigger a warning to your physiological system that there's a famine starting, with the result that your body will hang on to every possible ounce of fat. Create a small calorie deficit and you won't trigger that warning, and your weight will keep going down.