I absolutely agree with the argument that they are playing up to characters on the show, but I do have to say that while I have seen James May (Man Lab and that thing about toys he did a while back) and Richard Hammond (the building a planet thing and other science shows) being relatively likable, generally sensible and reasonable and very entertaining people, I have yet to see Clarkson as anything but a rude and rather unpleasant person.
Note that I found him interesting and fairly entertaining on QI, but I still found him to be an unpleasant person. Perhaps I should watch his war documentaries?