0.2g/100ml? That's a really small amount of carbs so it wouldn't have any affect on your current LCHF plan.
I reckon most people would put less than 50ml of diluting squash into a pint glass, even further reducing the carb content to basically zero. It's low carb not no carb; so you should feel free to enjoy some
I use the Robinson's No Added Sugar squashes too. It helps with drinking lots of water in the summer. The Lemon squash has zero carbs, and the Orange squash has only 0.6 gms of carbs per 100ml. They do use Apartme and Saccharine as sweeteners, which might be a problem for some.