UK ships will be up to Iran or Oman to manage. The same was as Russian ships through the Channel.
Iran has not ratified UNCLOS, but Oman has.
If Iran refuses to allow innocent freedom of navigation as per UNCLOS, then that will be a matter for the UN. Not unilateral action by the US. The US has also not ratified UNCLOS.
So if Iran refuse to allow passage to UK ships, or interfere with them in Omani waters, then they send their official letter to the UN. Then the UN decide on what action. Usually sanctions on Iranian ships.
That is how it is supposed to work. It is reciprocal.