TD5 leaking fuel rail.

I'm just getting round to removing the cylinder head (15p) because of the dreaded fuel leaking into oil problem but before I go that far I was wondering if anybody could point out any other way the oil and fuel can mix other than a cracked fuel rail. I fitted new genuine pert seals and washers to all injectors and they are seating well so, I was wondering if I have missed something else?

Thanks for any info/help.

From what I've read about the problem, the two usual reasons for diesel in the oil are either a faulty injector seal or a crack in the head between the fuel rail and an oilway.
Other than that, there's not much else I can offer.

Thanks for your input... I presume that's an internal crack and not an external visible one?...