You're spot on... this is not the typical cowardly Muslim behavior... this is the behavior of folks who think they have a bomb, or will have one real soon.
If they already have the bomb, then why would they be asking London for it?
Iran is in a box. The Americans have slowly cornered them. We are on their East in Afghanistan and on their West in Iraq. Our president has labeled them as part of the axis of evil. Libya, which made Iran look rational with their wacky behavior for the better part of a generation, has now decided to play ball on our team.
Iran knows that within a few months of the Bush re-election, we're going to make our run at them. And so they have two cards they're playing.
First, they try to destabilize Iraq; thus making Bush look bad and undermining his chances for re-election.
If that fails, their second (and only other) card is the nuclear option. They're trying to buy a nuke from Pakistan, North Korea, or anyone who'll sell it to them. If that doesn't work, they're trying to make one themselves. If they get a nuke, it will prevent us from attacking them (maybe).
But what's the best thing to do if you don't yet have a nuke? Pretend you do. Act wacky. Whatever. Just make people think you might have it already. I think that's what they're doing now.
It's desperation we're watching.