Ok, have got my camera back, and while looking on Ebay for other ones, stumbled across Asahi Pentax London, a Pentax repairer who take on old cameras, including (according to their website) Pentax 67s. 'Halleluja!' I thought, finally someone who can take a proper look at my camera, a 645NII. Sent them an email explaining the problem, along with the photo of the negative. Their response? They don't work on 645s! AAAGGGHHH!!! FFS!!!! Apparently not many of them were sold in the UK, so the machinery to repair them was an unjustifiable expense. They did, however, give me the email address of someone else who would be a better bet to take on the job, so I forwarded them the email and photo which I'd sent to Pentax. Their reply? You can probably guess. They don't work on 645s either. They did however note I'd also sent the email to Pentax, and said they might be better able to help me. AAAAAAAGGGGGGGHHHHHHHHH!!!!!!!!!!!