Low pressure from hot water in bath

Hi Josh As long as it's only the bath mixer tap affected it will more than likely be the mixer tap catridge at fault (not opening fully and getting jammed or it could be the washer on the hot side causing the issue, these break down over the years and can cause that issue also. Very easy fix might be worth taking the cartridge out yourself and inspecting it save yourself a few quid. Best regards Scott

Hi Josh, I would assume that your problem lies with your boiler. How does the cold water compare to the hot water pressure ? Have you had your boiler serviced recently ?

see if any service valves are partially closed what supplies your hot water ie combi boiler ,or hot water cylinder ?, is your cold supply to this tap mains pressure ?, more information needed.

If you have tried another tap then I doubt changing the cartridge on the original tap will make any difference you’ve already checked the pipes for leaks and blockages and sometimes it can be crap or calcium build up however as you have stated you tried another tap; it could be a partially closed valve