I would be extremely surprised if that happened. However, I would like to see this challenge answered in no uncertain terms, release the sailors or ELSE
You can even see this reputation reflected at FR; everyone assumes that GB has some sort of capability to respond. In actuality, their naval forces are no stronger than Sweden's. They are worse than a paper tiger - they are nothing. That's why it was foolish to put their people at risk; what we're seeing is the logical conclusion.
I know that comment was off the wall in a fantasy context but all I see is Iran giving us orders, we the US and Britain cannot be manipulated even if it means sacrificing lives. Yes this sounds also like a jimmy Carter monologue but it also does not exclude all out dark-ops.
A combined Delt-SAS contingent goes in Iran, assasinates Irans leaders.
Or better yet we get a modern day "Dirty Dozen" to do it.
I could just imagine MS13 loaded up with modern weapons air dropped in downtown Tehran.