I blogged about this but thought I'd share the experience here also incase anyone else has noticed this but is unsure as to what to do. Doesn't seem to be a prevalent issue.
So, having come across a post on Flickr about a gentleman who was having problems with excessive hot pixels on his new 5d mkII at long exposures I decided that it’d be a good idea to test my camera out a little more extensively to make sure I didn’t have the same problem. Turns out I did have the same problem.