The fruit ones have a lot of fruit sugar in, which is a no-no, although some people think the toffee muller is ok as it is low fat. Personally I find them too sweet now, and I prefer to have control over the sweetness factor.
I have used the vanilla and toffee ones to make muffins with since day one and have had a consistent weekly weight loss but I have a huge amount to lose so not sure if that is why. I don't eat them daily though just use them for muffins which I make every three days. I use Total 0% with vanilla extract and sweetener instead if I want yoghurt and find that much nicer than Muller anyway! x
Try them and if they don't stall you then fine. Otherwise Total % or making your own yoghurt is recommended. Everyone reacts differently to dairy. It also depends how many a week you will be eating. I eat yoghurt with every meal therefore definitely couldn't get away with mullers.
I did Mueller Lights nearly the whole time. More at the start when losing rapidly and then any stall, I'd switch to only non-fat plain yogurt with drops of vanilla and Splenda instead. But as my family reminded me tonight - I made "Dukan Muffins" quite often and they were made with Toffee Mueller Light (they're looking forward to the return of those treats )