So hang on, let me get this straight. You pay someone to do a test on you to see if you pass before going for the same test, provided free by the company interviewing you? Why spend the extra money? You don't need to.
Can someone please tell me why you would waste money? What difference does it make if you fail at interview? You didn't get the job, move on. Try again.
Knowing what I know now, I wouldn't go out and pay for an IR before securing employment either.
Let's not get confused by what happens here - there seems to be a (not so) subtle implication that people are in some way cheating by seeing the psychologist outside the CHC process.
The psychologists involved are doctors and the tests they conduct supposedly test the various personality traits found to be useful in commercial pilots (you know, spatial awareness, problem solving, prioritisation etc) - the tests are similar to (and in some cases copies of) those used by various armed forces.
The psychologists provide a service to CHC to test candidates against various criteria (and to provide a pschological evaluation) and they offer that service to individuals too (for a charge of around 800 Euro).
If you go privately and do the test, then you don't need to sit the CHC test since you are already on file (presumably as a pass or you wouldn't be there) just like if you'd given a DNA sample to a private doctor and then went to a public hospital. The test isn't done twice - just once.
While in the ideal circumstance you're right about not committing to an IR without a job, that isn't how the employers see it. Most of them (CHC, Bristow et al) hold out for an IR in the same way as they hold out for a CPL and an hour requirement - they'll hire what the job market can provide. When there are no candidates with IRs, they'll provide them - if it one day gets too expensive to do a CPL, they'll have to provide those and so on.
As it stands you can get closer to a position by having your IR in hand when applying but you don't want to pay for an IR before knowing you can pass the entrance tests...
The way I did it was as you describe - I sat the CHC interview (literally the week) before the IR course, and got a pass. Did the IR and then after that did the CHC Sim. Test. Not everyone gets to do it this way - partly because of the timing involved (you need to book an IR nearly a year in advance in the UK right now) and partly because CHC don't have to offer an entrance test to everyone who applies - you might not get invited without an IR, but with one you may be more interesting to them.
So there are several reasons why people might pay for the Psychologist test up front, and it can save them money longer term - bear in mind for some people CHC may (appear to) be the only practical employer. It may also serve as a guide that if they cannot get through the CHC process maybe something beyond their control will preclude them from completing the IR or getting work at one of the other operators.
BG.