Noise's when turning the ignition on?!

This is just a precaution really, lastnight I got into my Exige to move it out of the garage after having been driving it for about an hour before hand. I turned the ignition on and waited for the usuall noises to finish (the resetting of whatever it is!) anyway the noise seemed to sound a lot different to usuall, it sounded as though something had grit in it or similar. I had filled it with SU Petrol a while before hand having got to refill. Could it be that there was some muck from the petrol or do you think it is something more serious. I turned the ignition off and tried it again and it did the same noise until I had started it and then restarted again. Sorry if this is a bit confusing.Regards Peter