Maybe, but not likely. Iran know full well the British have our full backing. US + British > Iran x a billion. Executing 15 innocent sailors would cause an overwhelming retalitory strike.
We might be low on ground troups, but we have more than enough planes, bombs and carrier groups between us to bomb that country into nothingness and Iran knows it.
Right now Iran is trying to make a big deal over this to distract people from their nuclear program, and it’s working. You don’t hear anything about the nuclear program now, just these British captives.