The wars that the US/UK may have lost in the recent past were political losses, militarily they destroyed their enemies militaries in record time. There is currently no military in the world today that could defeat or defend against a US/UK coalition (why do you think China doesn't just take Taiwan back by force), especially a country that ranks way down in the military strength list. The last thing an Iranian pilot wants to hear (as the Iraqi pilots found out, most of their fighters exploded midair just after takeoff thanks to US F-15's)is "cleared for takeoff", so I wouldn't be concerned about their aircraft being effective for anything (the US already owns the skies in the countries surrounding Iran). Launching a weapon of mass destruction on a missile would be suicide for Iran, so I highly doubt they would actually do it. The best option for Iran would be for the people to rise up and overthrow their crazy government, that way the innocent only have to endure civil unrest instead of being bombed back to the stone age.