GinSu -- When I looked at the film the printers gave me to proof, I didn't see any tint swatches. I shall ask if they can be put on and will try the advise you suggest. I fear it may be the pdf itself though, as they output other clients' stuff on the same roll and theirs turned out fine. :s
y2b -- I originally did my first image as a monotone in PS with the correct PMS applied, but my printer said black would be best for a 1c job, as Jez said. I'll do a version as a monotone and see if it's any better.
joe -- I haven't got much knowledge on colour profiles. Could an incorrect colour profile be the reason why the image changes slightly when a C,M or Y sep is viewed over the K sep in the seps preview?
What would be the one I should be choosing for my image? Do I apply one before I start editing in PS, or after, for the final save?
Do I apply any in ID, or as I'm exporting to PDF? I assume I would need different profiles depending on whether I created the photo as a monotone PMS or as a grayscale? I may have to be led through this step by step I fear.
I will try and attach the PDF...may have to be zipped due to maximum file size on these forums...
Cheers for the help so far guys

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