i fear you're right danny, and am just hoping for a clever trick from someone i think. the images aren't vectors and have been created in quite an unusual way designed for on-screen use which means i am receiving enormous tiff files at 72DPI and having to re-scale / re-size them and optimise to work with. they're now fine in CMYK at 300DPI but of course because they are created flat there's no separating the elements to recolour them with spots. they are spirograph style images with thousands of very fine white lines on a black ground, much too complex to trace effectively or re-create in illustrator.
not the news i wanted but i appreciate a second opinion - makes telling my client a little easier, thanks!