Identify the Noise - Round #2

Okay, I suspect I may be called paranoid on this one, as this sounds no
worse than half the diesels out there, but after the success and
ultimate expense of my last guess the noise post, I thought i'd give you
all another go.

This one is hard to describe. Its a pinging click kind of sound, its not
there all the time, but it seems to be there the last few days as i'm
parking up after the drive.

As I move the mic around the engine, the sound is clearest at the end,
which worryingly is the back left of the engine nearest the recently
changed timing belt/lower pulley. Surely not my brand new lower pulley?
Its nothing like the rattling sound of last time.

It would almost sound like a belt slipping if it was more constant, but
my alternator belt is making that noise when cold anyway, and given how
sturdy it looks its hard to get worried about that, the point being, it
sounds very different to this.

Okay, here you go:

http://homepages.which.net/~derek.hawley/carnoise2.wav

Opinions appreciated. Reminder (Peugeot 306 HDi '99)

Cheers,
Tom.