Help! Corsa CDTI Intermittent starting problems EGC valve?

Hello, I am completely useless with cars, for a few months now our car doesn't start if it has been used recently. Most of the time if the car has been used in the last hour when you turn the ignition all the lights radio etc work but the car doesn't start, you can hear a clicking. Once it's been left a few hours it will start fine again. Have been ignoring this problem for a while trying to avoid these situations but have been stranded a few too many times now! Father in law checked the car with one of the diagnostic things and it says no problem. We bought the car from them and they say a few years ago they had a similar problem and the egc valve needed changing. Garage said this would cost £250 to replace so just wondering whether anyone could advise me if that sounds like what could be the problem?! It is a Corsa cdti design 1.4. 2005

Thanks very much!