Hello Mary,
If are looking for an 'emergency' weight loss I did the Atkins a couple of years ago. I lost 4 stone in about 9 months. It does work but I have put some back on, also you need to like meat because you eat a lot of it on that diet!!
If you want long term I would recommend Yoga and a vegetarian diet which I am now doing and it is much better for you than the Atkins!
I do know some people from work who have been to Slimming World and were quite sucessful. So it might be worth a try.
I think we have to find the thing that works best for us individually. Give it a go, I bet they do an introductory period where you could try it out.
I still recommend Yoga though

good luck whatever you choose.