RTR,
just to re-frame what the CAA can and cannot do with respect to safety.
If they have a reason to believe (and if that belief is reasonably held), that there is an issue with respect to either aviation safety, or safety within the cabin for cabin crew, customers etc, they can do what the hell they want to do.
I've seen the Inspector's pass terms for both the AviationSafety Inspectors, and the H & S Inspectors.
All the Unions concerned know this. The Unions asked for it. The H & S within the cabin did not come within the CAAs remit until about 4 years ago. The EU gave it to the CAA to "regulate/manage" at the request of the EU TUs.
Their actual powers to effect entry and to seek facts are quite draconian, and if anyone wants to/tries to, get in their way, the individual is committing a criminal offence. Not a civil offence.
The CAA do not brag about this, but when I was in Aviation I was left in no doubt about their powers which are underneath their velvet gloves. We can moan about the cost of the CAA, but no-one doubts their safety record.