No point second guessing. You need to have a diagnostic check. You could buy a diy OBD 2/can reader off the bay for less than £30. OBD port under handbrake lever in side car, just plug reader into it when ECU light on & you will get a fault code.
A none Vauxhall garage will charge around £25 for a diagnostic check. I have an Astra & have used the forum below:- http://www.vauxhallownersnetwork.co.uk/forumdisplay.php?f=83
George.
December 2008