1999 Ford Galaxy turns over but won't start

Hi I have a t reg ford galaxy ghia 2.3 and its not cut out whilst driving but the past 2 weeks its been turning over and not fired up! I've noticed the light on the door flashes fast n that's when I know it won't fire up but if the light goes off then it does! It's very unreliable! I have read up on it n nearly everyone that has had the same problem mentions the 30 relay! I have spent all morning on the phone to scrap yards, parts shops and hartwells! Hartwells say they are £54 to buy if its the right one!!! I'm at a loss, my car was in at a local garage n they seem to think its the ecu which would cost approx £900 to fix! I only paid £800 for the car! Lol just wondered if anyone had any suggestions please thanks in advance