Hi, and thanks for the response!
(sorry, I don't know your name - I'm Eoin!)

The blade's fine it's simply that the synthetic Polypan film is too tough to cut. The blade on the Rondinax cuts upward into a thin plastic slot on the inside of the lid. The gap between the two sides of this lid is just a little too wide and the Polypan film, rather than being cut, is pushed upward and into this gap. This can compress the film on the film spool. The alternative to my fist suggestion was to narrow the gap in this slot is to put a few strips of insulating tape over it. I used about three layers. Then with a razor-sharp blade, recut the slit for the Rondinax blade to go through. This works for me. But the earlier suggestion is the best, less fuss and you never need to worry about wasting your precious shots and film if it won't cut!

Now, I heard about the Rondinax 35. Is that the one that develops the film within its cartridge? If so, I understand the results are variable at best. But I will look out for the Jobo - that sounds interesting!

Thanks again for your response! I'll battle on with this film, I really do like it and it's such good value!