funnily enough i am having this same problem - called the GP near our flat in Redhill and they said 6 months i need to be here before i can register. called another place and they said the same thing. once i realized they were wrong, i called back. again, they said the same thing. i said "i am on a hsmp visa, working full time, living full time, i am entitled to NHS care" they STILL said no! again, i said, i dont think you understand, i am PAYING TAXES for healthcare! still - they said no.
i called the other place and they said come on in and fill out a registration form.
needless to say i was more than peeved. i wont be going into the first place!