just wanted to thank all of you for sharing your knowledge. i've just got my gas ticket and although i'm safe and full of theory, i don't have your experience when it comes to actually fixing things. my brother's xmas day was rapidly going down the drain when his boiler packed in just before my 96 year old gran was about to arrive (-5 degrees) and muggins here had to fix it. a quick look on the forums and the kettle went on - frozen condense (horizontal and uninsulated). 10 minutes later and i'm a hero. it warms my cockles to make a difference. THANK YOU ALL