Engine turning over but it aint firing? Then next time you try it sometimes works?
Then read on:
RAC guy tracked this intermittent starting problem to the crank sensor. The sensor sends a 0.5v pulse back to the ECU and located beneath the inlet manifolds. The connector oxidises and the tiny signal does not get sent to the ECU and so the ECU does not activate the injectors and the car does not start. If you wiggle this connector it will start OK.
So now you know why your Exige does not start occasionally.
John.