MInes been making that noise aswell, but recenlty i had my dual mass flywheel n clutch replaced by Doncaster Gearbox Services, and i got them to have a look at my starter. All they could see wrong was that it had become dry, which was causing the noise as it retracted from start up.
But as they told me, it'll be fine for a while yet and only replace when your sick of the noise or it starts causing problems on start up.
its a bit annoying but i'll save the money till it needs t be spent, its already cost me a grand and ive only had it 4 week!
Browny