Firstly let me comment on the topic of the thread..
GB has not ruled out Military action being required to solve the problem, however he did say that it was his wish that diplomacy could win thorugh and that he would ensure that military action would only be considered if and when all other avenues had been exhausted.
OK so he may be sabre rattling, and this is obviously for Ians benefit, but equally he has set his stool out early and basically rulled out military action as getting through now would be very difficult for him. Lets not forget that there are some 20 nations with Troops in Iraq, and these would be at risk if America went after Iran, so they would need their support for any such action, and that is unlikely without some real proof that Iran actually has a Nuclear Weapon.
The dubious "intelligence" that took us into Iraq would not be trusted at this time, Bush must be very aware of this, so I think Military action is highly unlikely.
Now, regardling the Nuclear program. Please don't believe the high tech lies that come out of Western Governments. I do not have a Nuclear reactor, however if I had 2kg of U235, I could actually enrich this with equipment I can buy in the high street and get about 0.5kg of U238. Now the amount I have would only be enough to make a Tactical size Nuke, about 2kT equivelent, but it would still be a Nuke.
However if you have ion excess of 10kg of U235, then you can actually use that to make a crude Fission device that would be around 12kT of explosive force.
You do not need centrifuges or other such high tech equipment to make a Nuke. Remeber that the US dropped two different bombs on Japan, one was using Plutonium 240 (Pl240) for Little Boy, the other used Uranium 238 (U238) for Fat Man.
The U238 was enriched from U235 using a partical accelerator in Hartford.
I have three similar devices in my home, and ebing an electrical engineer I know how to adapt them for the enrishment process. It would be slow and dangerous, but achievable.
Why have I explained this? Well If Iran wanted Nuclear Weapons, they do not need the Nuclear Reactor for this purpose, yes it is simpler and safer, but not a requirement.
I personally do not believe the Iranian plan to build Nuclear Weapons.