I have just started having the same problem with my 1600 TDCI. Owned my car for 4 months now, and am used to the stop start system only working when there is no heat/aircon/lighting demands, etc. but it has just stopped working. Even after a long drive (200 miles) when everything is up to temperature, and battery well charged the engine no longer cuts out when car is at a standstill. Also if I press the on/off over-ride button, the dashboard "@" symbol doesn't illuminate anymore. I am sure the problem started to happen when I forgot to turn off ignition (after coming to a halt and the engine did cut out), before opening the driver door getting out and then turning off the ignition. So if anyone knows a trick or two to reset this function that is baffling my local dealers, I would be grateful.