GPS coordinates should be able to pinpoint the position of the British boat to within a few yards. As to the Iranians, I think they have fucked up. That was a bad move on their part, because if they don't release the Sailors/marines, they will pay a penalty they may not want to risk having to pay. I think they will find themselves outside the community of nations. Notice that even the EU, often fast to speak against the UK/US involvement in the mid-East were vocal in their condemnation of the Iranian move. Bullshit 'confessions' from people who have been captured are seen as such by most of the world. Iran is trying to 'pump up' its own citizens to have them support the present government while the sanctions tighten. And tighten they will. Meanwhile, no Iranian foreign government official will be safe anywhere but Iran, and even then, some of the Spec Ops folks may be given license to have the Iranian government see things differently. The best move the Iranians could make right now would be to release the prisoners. The men being held serve no useful purpose for Iran. They are, in fact, fast becoming a liability. The problem has always been one of "when you grab a tiger by the tail you'd better have a plan in place to deal with its claws". I don't think Iran does.