I'm looking for a Vectra SRi, 150 BHP diesel, got to have the XP pack.

I've looked at a 06 reg which is the old pre-facelift model, can tell by the headlights but I've also seen a 55 reg that is the newer facelift model.

Why would an older car be the facelift model and, apart from the headlight design, are there any more differences?

Thanks

Bezza