Well the Sainsburys website has the carbs recorded as 7g of carbs per 100g.. personally I wouldn't use it but why not test before and 2 hours after eating and see if it has an effect on your blood sugars?
If you are are eating a low carb diet, then you shouldn't really be bothering with low fat products - it's called LCHF (low carb high[er] fat) for a good reason - fats and oils replace the carbs for your energy resources. So just stick with full fat yoghurts.
So not much difference then. The Sainsbury's low fat must have no added sugar, just the difference from the lactose in the milk then?
So unless the op particularly is looking for extra fat, no real issue. I'd prefer more chicken for my meal myself to be honest, but I do avoid saturated fats if I can, to be fair.