http://www.answers.com/topic/stuart-lockwood
About the helo I do believe it was a anti sub type from the British ship. I saw video id by Iranian sources as video from the capture which showed a British copter shadowing the group of Iranian ships with the Brits taken captive.
It would make sense a destroyer would carry an ASW helo, but I wonder if it did have some surface warfare capability. Certainly the destroyer did.