Hi am not to sure if am posting on the right thread but ill cut the story short I have a mixer shower and the hot water pressure is low I have spoke to a few people and they say get a water pump

I have spoke to a few people and they say get a water pump
that's not the solution. What you have is trash blocking the hot water inlet port on your cartridge. The solution is to turn the water off to the valve, open it up and remove the cartridge. Checking clean the inlet ports. Now turn the water back on for a few seconds to flush out the supplys. Reassemble and test. Good luck, Tom