My experience and judging by comments elsewhere, it is partially the luck of the draw.
My 7 failed its first IVA earlier this year. My examiner was a nice chap and we chatted a lot whilst he went through what he had to go through. The regional supervisor who accompanied him was also friendly and a bit of a petrol head.
Whilst they were pragmatic on certain things (rear visibility, exhaust noise level), they did fail me on five (yes... 5!) things:
- dodgy brakes - rears locked ahead of the fronts (why Caterham missed that in the PBC I don't know but...)
- no bonnet catch covers (Caterham returned the car from its PBC shy of them, so that was not unexpected)
- misaligned headlights (yes, cue another comment re Caterham, PBC, WTF etc)
- sidescreens lacking an 'e' mark
- indicator visibility being not to standard
Having looked up the exact standards online, I was able to call to he test centre and leave a message for the examiner. He called me back promptly and I talked him through how I thought he'd misinterpreted the rules and that the indicators were OK. Graciously, he agreed. He also said it'd be fine to represent the car without the sidescreens (and hinges) and to adjust the headlights using their gear at the retest. He also said the brake issue wasn't just down to a lack of bedding-in but something more intrinsic in the design/set-up.
Meanwhile, Caterham got the catch covers and some more aggressive front pads to me in time for a retest a week later. The pads did the trick after a circuitous route to the retest to allow plenty of heavy braking to bed them in.
This story is not to worry your mate at the strictness, unpredictability and inconsistency of the process (which I am sure others will corroborate) but that the testers (well, the ones at Yeading I met were!) are approachable, very helpful and whilst they've rules to apply, they are on your side and want your car to pass.
Whilst I was grumpy with Dartford having not checked the car thoroughly, at having to take the time, spend another £90 and not be driving my 7 as soon as I wanted, I did come away being fully confident that the car was safe, legal, to standard etc. I would have worried if the VOSA chaps had given it a cursory look-over, even though I was confident I'd built it well.