I had problems with my TD5 a lad said it was my fuel pump on its way out, I took a look on the internet and theres actially two relays under the drivers seat, I think one was sticking or not working, I replaced one, sometimes taking them out and putting them back in worked..
The symptoms were it just turned over and wouldn't fire up, sometimes had to keep turning the key then it would randomly start...
Take a look at your relays might be a long shot, but could be an easy fix..