Hi, making sure the pump,valve, vessel and of course your boiler is ok , thrn please try the following.
The answer was, I tapped all the pipes gently but hard enough to descale/make the lime scale come off the coiled pipe where the hot water goes through into the immersion heater to heat up the water inside the immersion heater and also to clear the pipe holes just incase they were blocked or part blocked.
This was tested and tried today and it worked with an amazing consequences, we now have hot water coming out of all our taps when switched on and also most important our power shower with the correct pressure.
We were going to replace the immersion heater, byut now we're thinking why replace something that works.
Are we luck or what!!!? " What ever your answer, your probably right"
now clean Dan and clean Sharon, March 2009