I've made some scans with Digital ICE enabled and disabled, and I've put the resulting scans athttp://www.dvmp.co.uk/digital-ice/
I thought it would be better than attaching the pics here in the forum.
You can clearly see the blotches.
Have you seen anything like this before?
I remember developing these negatives myself, and getting them printed at Boots. It was the first few times I had done ANY developing of negatives, but the prints that came back seemed OK.