It's probably severely overhyped from what you describe.
Dirty Bombs are based on the rabid fear of radiation. The greatest threat from a dirty bomb is the panic itself.
Like chemical weapons, any time and money a terrorist spends on dirty bombs instead of high explosives is time that terrorist is wasting.
"It's probably severely overhyped from what you describe."
The way the terrorists prepared, how the Gov. covered their tourism $'s, how the CELLS work and things like that is what has me most shaken.
The bomb just went off.
That's pretty much the angle the movie took - it did make areas of London uninhabitable for up to 30 years though. Property values in the city as a whole plummeted as well. A dirty bomb would probably have the effect of convincing up to 1/3 of the population to move out of the city.
As you said the threat is more psychological than physical.
There was a very thought provoking line in the movie. When interrogating one of the planners, an interrogator pointed out that the bomb would hurt more muslims as the west would be sure to retaliate. The terrorist was unfazed and replied, "We expect retaliation - it unites us and divides you."
Dirty bombs are for the most aprt harmless, unless of course they seed the explosives with something really nasty like anthrax or cesium.