Iran seems determined to ratchet up the pressure; it has announced new exercises for the Strait itself:
State media: Iran to hold military drills in the Strait of Hormuz - CNN.com
Presumably the objective will be to freak out oil tanker captains by firing around, though not at, them, perhaps causing a traffic jam of tankers at both ends of the Strait; it won't be foolish enough (one assumes!) to actually fire on a tanker, but presumably one of the aims is to call the UK/US's bluff and ask what exactly they intend to do to keep the strait open.
It's another move on the chessboard ...