Nige
You might have requirements to do the course but you do not have to do the course to perform EST.
So unfortunately the answer is "yes" any T, D or H can perform an EST, but it is a bad employer/manager who allows this to happen. Or one who is cost cutting.
As for the proficiency/qualifications/abilities of the external companies who came in to hospitals and safety test everything in site - hopefully with the exception of medical equipment - well.....?
Robert
PS
so they need a solid understanding of what they are testing for, not simply pressing a button and looking for the pass symbol.
and some more experience techs as well. I have seen people testing equipment with it switched off - and by that I mmean not just a soft switch, the hard mains switch