Frankly, I would be astonished if either Bush or Blair entertained any thoughts of military action against Iran, particularly after the events of the last few years. It would be political suicide for either of them, I think.
Neither country has the resources or the political will to do it, after the events of the last few years.
Both countries would need to get the electorate onside if they were to attempt this, and I think that needs much more evidence of provocation and/or warmongering by Iran than has been currently shown.
Then there is the international angle... both countries tried assiduously to garner UN approval prior to the invasion of Iraq. They would find that even more difficult now, after recent events, and would require substantially more evidence of any alleged destabilising threat from Iran.