Cut off HOT water to bath water faucet Only from Hot press?

Hi Guys Im trying to cut the hot water off from my bathroom bath faucet only. We have an electric shower so just want to use this and keep the hot water for sinks. But someone keeps getting baths and using up all the hot water.
I looked under the bath and there is no isolation valve at all. But i do notice the hot water pipe that supplies the bath faucet i want to turn off seems to branch off to behind another wall. I was going to mess around with the valves in the hotpress to see if I could stop the hot water from there but Am i right in thinking the only way to do this is have an isolation valve installed at the bath faucet point to avoid cutting off hot water to elsewhere along the branchline? Am i wasting my time playing with the hot water valves in the hot press, i dont want to shut off the hot water supply to other faucets? Or should every hot water point in the house have a valve/direct line from the hot water tank?