ok did it, how long should I run that for? I let it run for a few minutes, temps got to about 80 Celsius and fan had just started to kick on. both processors ran between 99-100%
That's normal. I don't have any overheating problems at all. I can run Skype, run two SD movies at the same time. I've actually done the yes command in two terminals and ran a movie and I topped out about 82C. The Fans run full bore, but it doesn't do a core shutdown.
Lot's of folks like to bash and commit this as normal, but it definitely isn't. Take it back to Apple and let them fix it / swap it.