This is exactly what I did. As well as identifying and clearing the fault that I was there for, I identified 2 x C1 (the 460 volts in the lighting circuit and the missing blanks in the board) and did something about them. In both cases I did not 'repair' properly, but made safe with the materials and tools I had at hand.
There were C2s as well (the obviously overloaded kitchen circuits) which I did nothing about, except speak to the landlord about when I next saw him, and strongly recommended their improvement.
Interesting discussion.
I note on the HSE web site, a few things.
Firstly, HSE is not directly responsible for pubs, clubs or restaurants. The local authority has that responsibility.
HSE also advices, that if you have safety concerns, you should report them to '
the person in charge of the work, your employer, your union or employee representative'. Failing that, you can report your concerns to them via an on-line form, or ring them and they will complete the form for you.
In this tragic incident, the case was bought by the local authority. It was also mentioned in the court case, that the landlord, had been previously warned to take action by the local authorities.
From my limited knowledge of HSE, their role is of encouragement of health & safety in the workplace and enforcement last.
I think the distinction of carrying out emergency repairs on a property, and carrying out dangerous installation work, is clear. I can't see anyone being prosecuted, for making something safer, than it previously was. And showing due diligence, by reporting their safety concerns, to the person in charge, as suggested by HSE.