Not sure how a Peter Hamilton book that's been out a year which I paid the princely sum of £7.99 in paperback for is still selling as an ebook at £12.50 though!
Hi Tim, have you tried WH Smith's ebooks section? They have most of Hamilton's books at £6.60. (I've used their site a little, but the search engine is dreadful!)
I also use Books on Board's UK site - they're just about the best at the moment, I reckon. (see this.... Night's Dawn Trilogy for £5.63 !!)
As others have said, Baen is fantastic - especially if you try the 'Free Library' button at the top of the homepage.....SF for FREE!!