Well he didn't actually say Iran could bomb the UK, although the open-endedness of the statement obviously had that connotation.* Either way, I and many others aren't falling for this one.
We were duped by Tony Blair; with his infamous statement that Iraq could hit us with a WMD within a 45 minute window. Not that many believed that either.
Our government is in a bad position though, albeit one of being between a rock and a hard place. To get greater IAEA cooperation from Iran, a potential 'deal breaker' would be to have the IAEA visit Israel in the same manner. I would hope that would be enough of an act of good faith for the Iranian leadership to be less hostile.
The problem of course is American intransigence: you can bet your life that the Americans will never do this, not for generations. It would appear as a concession, the pro-Zionists in Congress or in US businesses would oppose the move, and even if President Obama wanted to do it he would face the legislative equivalent of a firewall. Britain cannot realistically try to apply such pressure for an IAEA inspection of Israel either, as we would incure a diplomatic rebuke of such proportions from the US that our government clearly doesn't have the backbone for.**
Not that I've gone out and asked people on the street, but if I did the chances are that no one is going to be worried by the Prime Minister's statement, probably citing Blair and Iraq as still being fresh in the memory. The more informed Britons regarding foreign affairs will ask the question: "But what would Iran gain from attacking the UK?", especially without military provocation.
Answer: nothing.
*You do realise what source this is? It's The Sun and the Daily Fail, the most alarmist papers in the UK with the most irreverant, dim-witted and fundamentally stupid readership in the UK, ney, the western world!
** I know, the solution would never be that easy. But the only way for Israel to change is for the US to withdraw the level of support it gives Tel Aviv. A radical change in US Foreign Policy, essentially, but that's not going to happen any time soon.