The UK Bookseller WH Smith has been experiencing some kind of bug in its ebook store, whereby it adds DRM to all of the Kobo ebooks it sells, even the ones that are supposed to be DRM-free (like mine). Apparently, this is a metadata-parsing issue. I spoke to my agent and publisher, and WH Smith/Kobo came up with a good workaround while they fix the bug:
Kobo/WH Smith have come up with a solution that enables your e-books to still be on sale. The DRM wording has been manually removed from the WH Smith site and when readers click to purchase the book it forwards them to the Kobo site where it clearly states the e-books are DRM-free until WH Smiths is able to update their website which will be at the end of April.