You could always try substituting fat free vanilla yoghurt for a totally free alternative (Muller lite or Dr Oeutker are free, I think Yeo Valley might have sins but minimal) - I tend to have yoghurt instead of icecream these days. You can even make a sort of ice cream with it if you freeze it - not sure if you have to do any more than just sticking it in the freezer - there's bound to be some hints and tips on the site somewhere