It appears that Universal Music Group have persuaded HD Tracks to better enforce "regional restrictions" and they now refer to the users IP address, so the Paypal workaround no longer works for UMG titles and other labels under their umbrella. Unfortunately this blocks a significant chunk of their catalogue! Not sure what you're into but you can still purchase albums under other labels, such as 2L (mostly classical, great sound quality) and Reference Recordings, and I recently downloaded some Fleetwood Mac which I thought sounded really good too.
Not sure what Universal Music Group think they will achieve as they had me searching for Oscar Peterson's Night Train on the pirate sites since I was unable to purchase from HD Tracks. I hope we'll soon see a UK equivalent of HD Tracks but bet your life they'll be looking to charge £18 as opposed to US$18 per 24/96 flac download!
And the music industry continues to shake their heads and wonder why the pirates thrive.