I've just learned that UK retailer Tesco has surreptitiously opened an ebookstore at www.tescoebooks.com. I don't know how long it has operated, but I ran a whois search and the domain was registered back in October 2009. The site has probably been up for a while.
The ebooks are available in PDF and Epub, and they are encumbered by Adobe DE DRM. Prices seem rather high (from an American viewpoint), and worst of all, Tesco limits you to 3 downloads per title. Yikes.
Tesco also sells ereaders at Tesco Direct.