Following the earlier thread on 307hdi, here's my posting with almost identical problem. Mine is 2.0 not diesel, bought in March 2004 and right after it got a bit colder here (it was a bit under +13 deg. C) I started to have this problem: in the morning the car won't start. Just like that. It started after the 12th try, next day - after 6th try. Then it got warmer and it starts after 2-3 tries now. Indeed, it's like when the immobilizer blocks the wrong key and won't let car start. But I went to my Pug dealer and they did a thorough checking with their dignostic computer. No faults! So, if it was the immo it must have left a fault. The dealer says that there's no problem. And of course I cannot prove anything to them, because during the day the car starts well! Has anyone else seen such behavior? Thanx.
FYI: the Pug dealership told me that, after checking with their bosses in France, this is a common problem, and it's due to bad hydro-compensators (I hope that this is the right term) - for this particular range they replaced the manufacturer and it turned out that the pieces are faulty. So, they are replacing them all now.
