I agree with Bluetit.
Just because a diet is appropriate for weight loss doesn't mean it is appropriate for someone with impaired glucose tolerance.
If you test before and after the Slimming World meals, and discover that they are raising your blood glucose too much, then you can adjust them to lower the carb content.
It may only take a few simple changes to bring your blood glucose back into line, such as reducing your potato, bread or rice portions, and substituting them for more vegetables.
Everyone seems to have different preferences for their diets, so if you like Slimming World, and it is working for weight loss, then it is worth trying to make it work for blood glucose control too.