I was wondering after reading Asmits' OP.
Have I got it wrong that in order to obtain a schutzhund/IPO title you must do the OB,Tracking and Protection all in one trial?
That is correct. There are other IPO titles you can gain for doing just obedience or just tracking, but to get IPO I, IPO II and IPO III you need to do the tracking, obedience and protection all in one trial.
A bit like working trials in which you need to pass all of the obedience, tracking and agility to get the title you are going for.