i make fruit smoothies too (usually what i have for breakfast each day) and i've found that when u put the smoothie in the freezer for a couple of hours it turns into a sorbet sort of texture (more icy than frozen yoghurt) which is really yum!
my recipe is:
200g vanilla yoghurt (i use nestle french vanilla (the WW one) or yoplait no fat)
1/2 - 3/4 cup skim milk
5-10 frozen bluberries (the creative gourmet ones)
5-10 frozen raspberries (the creative gourmet ones)
1 tsp honey
1/4 cup pineapple juice (optional)
1/2 cup oats (optional.. e.g i add oats when i'm extra hungry at brekkie time - fills u up for way longer)
just chuck it all in the blender and blend for a minute or two.. when i'm freezing it i put it in one of those metal milkshake cups (they come with those breville milkshake makers, lol) cos it makes it freeze faster than if u used plastic or sumfn, and it stays extra cold whilst u eat it..