personally I think all the fat free natural stuff tastes about the same, you can add powdered sweetener to it, vanilla essence,both together or have it with sugar free jelly, all nice.
It is great for cooking with too, there is a really good korma recipe in week 4 when you can start cooking your veg which calls for yog.
You will be able to have muller light next week though.
I am not sure as I never asked, but they do a vanilla muller light, I can't see why you couldn't have it from week 2.