Ok few things for this fault check you have a good battery 2nd in some cases the starter motor takes to much power out of the battery to turn the engine over and needs to be replaced as cranking speed is very important on hdi engines to achieve correct fuel pressure its also worth checking the battery connections at both ends of the leads in rare cases engine oil is too thick due to lack of servicing causing sluggish engine rotation when cold good luck
Peugeot master technician
December 2008