Originally Posted by GeoffC
WHSmith have a site ...
And it's improved a lot since I first saw it. It's now quite easy to navigate and search, and each title is clearly flagged with the formats in which it's available. Best of all, it is dedicated to ebooks (but including audio books), so you don't get the search results crowded out by paperbacks and hardbacks (as you do with Waterstones).
The range of available titles isn't brilliant, but it's a start.