ATG wrote:

You actually think Britian would be confused as to where her soldiers were?

As far as the US and Britian goes, there is no need to lie about a reason to go to war, we have that already. We are not in open warfare with Iran, I guess because we are stretched thin. But the justifications are there.
The US and Britain don't quite yet know whether they want to 'go to war' yet. I can't imagine the British public buying it - detained soldiers or not.

As to Britain being 'confused' - they have a long and illustrious history of lying through their teeth to save face:
for just one example research The Guildford Four.  Their deliberate wrongful imprisonment is made all the more shocking by the fact that one of the IRA men responsible apparently handed himself in when they were convicted to their lengthy terms and the Brits still didn't release them.

As such, I don't have any particular reason to believe the story of either party in this case.