Hi, I have a problem with my potterton puma 100e (please don't say ask santa for a new reliable boiler!!) The hot water started to fluctuate in temperature. Not much and was only noticeable when the shower is running. Recently the locked light came on and needed a reset.This has happened a few times but always works fine after 1 reset. The other day i noticed the system pressure was at the low end of the green so i topped it up towards the top of the green on the dial. When the heating came on the pressure went sky high into the red and the boiler overflowed thro the overflow pipe.The locked fault seems to have stopped now but the pressure still goes high into the red whenever the heating comes on but drops back to normal when it goes off.