As ericmark says, PAT isn't an end in itself, it is part of a system.
You don't actually need a dedicated test unit if you have other test tools (insulation resistance and continuity) and only a few items to test. However, once you stray away from a unit where you select the type of device (Class I, Class II, lead), hit "Test", and the unit gives you a good or bad indication - then you need to be able to determine what test parameters to use and how to interpret the results.
The actual test if very simple - if you apply a voltage between L&N combined and earth, does any current flow (shouldn't do); if you stuff a current between earth pin on the plug and the device casing, is there a low enough resistance to trip protective devices (fuse in plug) and avoid dangerous voltages. The issue is that without training, you won't know what voltage to use for IR on different devices, what current to use for continuity (if there's a choice), and what results are acceptable.
My training only qualifies me to use a "go"/"no go" tester, though I don't suppose it would be hard to learn the details above if I needed to.
In any case, inspection is 90% of PAT - I don't know the actual figures, but it's some very high percentage of faults are found by inspection rather than test. Only the other day, on a customer site (I was doing IT work, not PAT) I found two moulded 13A plugs where the cable sheath had pulled back leaving the cores exposed - one was a "kettle lead" on some IT kit (pulled the fuse out of the plug and cut the cable into short bits), the other was on their Henry vacuum cleaner and I advised them to have a new plug fitted.
Teaching operators how to do a very basic inspection each time they get a piece of equipment out to use would be a good start. Just a few seconds to see that :
The plug is still fitted to the cable properly (ie cable not pulled out).
No cuts or worn through patches on the cable sheath.
Cable still entering the unit properly.
And nothing broken on the unit.
Get operators to do just those check and you'll catch the majority of things a PAT would catch.
Good luck with that, at work we can't even get people to not drive the cars with obviously almost flat tyres or low (coolant or oil) light on the dashboard
The concept of actually inspecting anything is completely foreign.
And just for good measure, once you've bought your PA Tester, you'll need to pay to have it calibrated every year. That's a nice little earner for someone - you can easily pay as much for calibration in 3 or 4 years as the unit cost