i was about to try and do what he has done, register with another email address but use the same us iTunes account. The plan being no iPad/iphone/mac use of HBO Now. Well i have had a surprise.. i clicked "join free trial" in the HBO Now app on apple tv.. and it gave me a message like "congratulations, your account has been reinstated" referring to my us iTunes account email i think. and HBO Now is working on my apple tv.
i hope it works.. iv'e heard stories that it can work on the apple tv undetected but you will get detected if you use HBO Now on other platforms.
Are you experiencing any problems with video playback at the moment?