Jaguar S Type Urgent Advice Required

I am picking up a 2000 S Type tomorrow to replace my knackered XJR.
When on the test drive, the car ran very well but at a set of traffic
lights the engine management system warning light flashed on and off
twice. There were no problems with the car and the warning light
didn't flash again. Was it because the car was cold? It had been
sitting on the forecourt for a while.
Am panicking, urgent help required before 12.00 GMT.

Cheers

Richard