if ure with the AA get them to come and have a look at it...they carry resetting kits.
or you can try this but iu can't guarantee that it will work......
unplug one of the leads from battery terminal ...leave it disconnected for a few mins and then reconnect it BUR REMEMBER to put the keys in your pocket before you do this or the car may auto lock when you reconnect leads and the other thing is if the stero requirea code it may requaire the code agaain when you reconnect leads...if you don't have the stero code then try at ure own risk.
i've had my engine light go off (reset this way however, it did come back and turned out it needed an oxygen sensor), if it turns on again then it means it needs looking at by someone who has a proper kit