My ID confused with another

Hi I've just changed my password, because I'd been away from Apple for years. I tried to sign up to AppleTV's free trial but there's a conflict. I logged into my Apple account on my old iMac, got a welcome dialogue box, then just a blank window and an endlessly spinning dial (tried this a couple of times, different browsers). Behind that dialogue box is an Apple TV screen offering me a free trial in UK pounds, not NZ$. I checked the account info and it gives a address in London, when I live in New Zealand. I tried changed it but the country is greyed out. I can't change that. Clearly my account is now confused with another... How do I get this resolved?