Hi I've looked at similar posts but not seeing anything exactly the same as this. A while back we had a friend do a repair on our toilet and at the same time he put in a stop valve because he said we didn't have one. Not too long after the water in the hot tap stopped running. I can't be certain they're connected because I didn't pay attention to how long after it that happened so I'm not ruling out a coincidence. Someone advised me to turn the cold tap on, open the hot tap and push the water back up but that hasn't helped. If it's any use, we're on a conventional gas boiler and its upstairs. Would be grateful for any pointers.