I have now used an Autel scanner. The code P0133 appears which indicates a slow response on the 02 Sensor circuit. I turned the MIL light off and drove fifty miles. Then I stalled it in Rodez and the MIL light came back on. Turned it off and returned fifty miles home with no recurrence. However occasionally the engine runs quite fast at start up and may stay like that for 10miles or so before idling normally at 900rpm. It has only started to do this as ambient temperatures increase: during the winter it was fine. Has anyone else experienced this?