I have an Ideal Cmbi boiler, just over 2 years old. 3 Days ago we turned the heating on and and now it will not turn off automatically via the thermostat. I have to physically turn off the boiler to stop it from keep pumping out the heat. The thermostat (Drayton, basic dial one) does not click at any point (as it should when reaching the desired temperature) and is set to the lowest temperature, but the heating continues to pump out. Does this sound like a broken thermostat, or something more serious? Thanks in advance, and i know i am just being tight but I do not want to call out an engineer before trying the cheapest option of replacing the thermostat.