i think i'll be correct in saying that a diesel loom won't supply power to the stop solenoid whilst cranking the engine over (might just be the ignition switch tho)...
whereas i believe the petrol one will obviously continue to supply the power...
that is, assuming there's no difference in the ignition switch itself
my diesel needed a seperate switched supply to the 200Tdi solenoid (mine's a Series Bitsa)...
to be absolutely sure on your requirements i'd speak to the folks you're intending to get the loom from and ask about the ignition switches to find out if there's a difference (cos then if there's an error you may have some comeback)
there is also differences between early Series wiring and Series 3 wiring so make sure which model you're talking about when sorting it