Thanks, that was a great response! After a thorough clean and swap the lens appears to be significantly sharper.
There were some marks on the taking lens which would not budge, the viewing lens was totaly clear though.... i swapped the two over (there were no shims - had certainly been done before!) and performance has definately improved.
It seemed to be diffusing very slightly before, which i think would have been caused by the marks on the lens - i have an enlarger lens which gives similar results.
I do find focussing a bit more difficult - but overall this is a camera im much more comfortable with than the 645. Comparing similar prints of the same grade from the 645 and c330, i think there is a contrast difference - certainly a different general look - i'll try ajusting development a little.
I love the close focussing ability!