Thanks for your advice, Nicolas.
I am aware that there are many lens-related metadata tags in exif, however when I compared an uncorrupted file with a corrupted one from the same session the only significant difference I could find between the two groups of metadata was with the LensModel tag (I have described the contents of the tags in my previous post).
This is why I asked if Lightroom read the LensModel tag when displaying lens information. If it does not, then I would love to know which bits of the exif file are used for this information, as this may help myself and others solve the problem which we have been experiencing (as described above).
Another somewhat uncomfortable question is "where does the corrupt data come from?"
Is it generated by the camera?
Or is it generated when the file is copied from the camera to the computer?
Or somewhere else?