As to the '70's, I know somebody pointed this out before me, but I think it's the only way they can plausibly use the "cousin from England" aspect. In 2011, it would take no time on the internet to debunk Barnabas' story
and there would be no way to keep the prospects of a vampire local in the days of YouTube and cell phones with cameras and video capabilities.
You know when Eva Green said she's blonde, and very cool in the 70's. I took it that she was talking about LP and not her version.