Why does my peugeot 207 sw estate engine carry on running for a couple of seconds after switching the ignition off?

The phenomenon you're experiencing, known as "dieseling" or "run-on," typically occurs when the engine continues to receive fuel and air after the ignition is turned off. This can be caused by several factors, including carbon buildup in the combustion chamber, a faulty ignition switch, or issues with the fuel system. Additionally, if the engine is running too hot or if the idle speed is too high, it may continue to operate briefly after the key is removed. It's advisable to have a mechanic check the engine to diagnose and resolve the issue.