I have a Worcester Greenstar 37CDi and I'm having a few issues, the timer is set to come in at 17:00 but it sometimes doesnt come on, it's all set correctly and occasionally it will work. When it doesn't come on, nothing gets it going, not a reset or an off/on, then only way it triggers on if I turn the thermostat, as soon as I turn it, the boiler fires up. The pressure is rather low on the boiler too. In the red just above 0...could this be the cause of the problem as it been working fine before. I don't have the key to re-pressurise it, where can I get one, or is there another tool that can be used? Thanks for any help...