Well I'd be happy to offer some advice, I'm a personal trainer, kettlebell certified, and a group fitness instructor, and most of my clients are women around your age, so I'm used to helping people get on the right track. I live in America so I'm not too familiar with how much a stone weighs, but thats not really that important anyways, because it wouldn't change my advice.
If you really want to tone up, and lose body fat, then running on the treadmill is really not the most effective method. It is a common mistake to believe that aerobic exrcises such as jogging, cycling, etc is the best way to burn fat, because it simply is not. Performing moderate intensity aerobic exercise for extended periods of time can actually be counterproductive toward maximal fat loss. The absolute best way to burn fat and tone up simultaneously is through high intensity anaerobic interval training.
When you train short bursts of intense exercises, not only are you putting your body under a lot more stress(stress is what makes your body adapt/change, which is what you want), but since it is performed for shorter intervals of time you do not suffer as much free radical damage to your cells. When I talk about stressing your body, I'm referring to the intensity of the exercise. If you truly want your body to change(become leaner), then you have to stress it in such a way that it is forced to do so, and moderate aerobic exercise is not the way to go for that. Also remember that even after you spend an hour on the treadmill, you've probbaly only burned between 200-300 calories, and within a half hour of stepping of the treadmill, your metabolism drops right back down to a sedative level, whereas if you train with high intensity anaerobic intervals, your metabolism can stay elevated for up to 72 hours. Its really quite a difference.
As for what to do for this type of anaerobic training, I use many different system for my clients, but I almost always include some sort of kettlebell training. Have you ever trained with kettlebells before? If not I'd be happy to give you some good information on them as well. But really what you want to do is perform short bursts of intense exercises, say 30 seconds-1 minute worth, followed by a short rest. An example would be sprint intervals, or kettlebell swings/snatches. This may sound intimidating a lot more work than running on a treadmill, and usually it is, but the difference int eh results are incredible, and your hard work will pay off. Like I said, most of my clients are around your age, and I have gotten many of them into the low teens and single digit body fat percentages. I hope this helps and let me know if you want any more information about specific programs and/or kettlebell material!
))