This is what I was thinking - the film is not lying flat. I'm using f/22 and a tripod, so I should be getting max depth of field.
I realise I can just crop in the darkroom, but I liked the effect of printing a big rebate and showing it as a true 'panorama' rather than just a cropped 120 image. Plus you get the extra 6 frames on a roll. If I get around to subscribing I'll post the images.
I'll give it one more go - if it doesn't work out, expect to see a Mamiya 7 panoramic kit on ebay soon. Maybe I'll put the money towards the Mamiya 7 polariser filter kit - has anyone used these and is there a big advantage over using a straight screw-in filter? Is it worth the £100+ price tag?