Personly I think keeping to "A New Atkins For a New You" is a better option then the shakes as I like "real food". (But the shakes would work well with something like the 5:2 diet where you have very low calorie and carbs for 2 days each week.)
Personly I think slimmingworld is far too "high carb" for anyone with Type2, but as they do get everyone to give up sugar, they can be a step in the right direction for many people. I don't know of any nationwide diet support groups that use low carb, however, remember that the likes of slimmingworld make their money from people keep coming back.