OK, so I've read OverTheHammer's review on Slimming World. I haven't been to SW but I do know that it works for some. There are people in the office who got on very well with it and have successfully lost weight.
However ......... as a compulsive over eater, I don't get on with the concept of 'free foods' and 'eating until I'm comfortably full'. I don't recognise the feeling of being comfortably full and tend to overdo it: not by much probably, but enough to have led me to be well overweight.
So ..... WeightWatchers. On this programme, I count SmartPoints (SP); it's basically like counting calories but they just zhushed it up a bit—to give it a USP, I guess [blsuh] I get so many SPs per day and do my best to stick within the limits.
I go to the class, which is a half hour group chat, every week. I find this incredibly useful and well worth my £5 per week. It's OK saying 'it's a con' and 'just do it yourself' but I'm a human being, with all the trappings of weakness and frailty, and I do get led into temptation. The classes keep me on the straight and narrow; they really do 
I started out at 15 stones (size 20). I'm now 8 stones 12lbs (size 8). It works for me is all I'm saying.
Join a group, OP, whether it be SW, WW or some other. Try it and see how you get on. If it's not for you, try another. You'll find the one that suits you.
Wishing you lots of luck. S x