Hello there. My boiler is a vokera compact 24, 3 years 8 months old. Recently my wife reported that whilst showering the water was going cold, then hot again, then cold etc, for periods of about 20 - 30 seconds.Yesterday 15.02.2010 the boiler was providing no hot water at all. The red light is on and I have reset the appliance repeatedly, the green light initially comes on and there is a little hot water, perhaps for about 30 seconds, then it goes cold again, and the boiler goes into ' lock mode ', the red light permanently on. The pressure is fine and have had no problems at all prior to this. I called vokera but was left on hold. I consulted a friend who advised me to contact the person who installed the boiler, which I did and I was told he would send somebody to 'sort it out'. Nobody got in touch or called, any advice or help greatly appreciated, better still, a reliable , knowledgeable boiler repair engineer in the leeds area.Thanks. Ed.