As a followup to our notice that, in contrast to the way the title's been used on JKRowling.com, there will be a hyphen in the American edition of HBP, we've just confirmed it will also be in place in the British edition. The book will be Harry Potter and the Half-Blood Prince no matter where you buy it. This decision was made to be consistent with the use of the term in rest of the series.
I'm really relieved. I've not been able to sleep nights wondering about that hyphen.
Um. Or not.
Erm, I've actually never wondered about it and I kind of think that those who do? Have waay too much time on their hands. (Apparently there's some definition thing involving vampires that makes it Oh, So Important, but. I don't get it.)