I have an issue with hot water pressure in the bathroom. I turn the shower hot water on only get a bit more than a trickle come out. I have to turn on the bathroom basin hot water fully on and fully off than I get a full shower pressure. I was thinking it could be the pressure regulator. Any ideas?

I was thinking it could be the pressure regulator. Are we talking about a PRV,(pressure Reducing valve) ? Or do you have some sort of regulator on your hot water system? Let me know, Tom