Normally this kind of story gets filed under 'slow news day', cross-referenced with 'bending over for public relations staff', but we have some advice to give you. Although today the phone goes on sale in O2 stores, note that it's only on sale in O2 stores -- not online. And it's online you should be looking to buy this bad boy from.
The reason is simple: O2's online deals are way better than its in-store deals. Often you'll get double the inclusive minutes or texts. We nagged O2 for some details, and a spokesperson initially told us the HD2 is to be "in-store only to begin with" (emphasis our own).
A smidge more nagging got a confirmation that it'd hit the online store in "the next few weeks". And frankly, we'd be tempted to wait and see what deals you're offered online. You may end up with a significantly better contract if you hold off.