The problem with that disaster scenario is that it's very likely that the
Gulf Stream isn't responsible for Britain and Europe's warm weather:

http://www.eurekalert.org/pub_releas...-crr012203.php

So even if the Gulf Stream does shut down, it won't result in any ice age,
though it may make Britain and Europe a few degrees colder. But that will
just counteract the effects of Global Warming so it'll all be great.

Bob