Unfortunately the 12th has come and gone with no HTC HD2 materializing on either O2 or T-Mobile. The rumour currently is that the device is awaiting a final ROM, which is set to be delivered only on the 18th.
The latest dates for release sets the 22nd for O2 and the 6th November for T-Mobile UK. I have telephoned T-Mobile customer services myself, and while the device is now showing up as coming soon they were unable to confirm the date.
The device is however clearly floating around inside some stores however, as this picture, clearly taken inside a phone shop, will attest to.
Information sources for the great HTC HD2 thread on XDA-Developers here.