Ok thanks Phil,
I might just use the MIE files for Acdsee and and XMP for LR information to distinguish between them. That way I can keep filenames the same , it'll avoid renaming sidecar files and making mistakes when one goes into auto mode.

I've submitted the Acdsee bug report btw. I'll let you know if there's any positive response.

It'd be interesting to know how many versions of Acdsee that Exif misnaming has carried across. They might have been doing it for years. :-)