How do I go about this?

[ericmark]

You're showing your age, I know 50 volts to earth tripped them, and parallel paths could stop them working, but when found they were just ripped out, never did test one.

 

[flameport]

inspection and testing of domestic properties and/or is that not something I should venture into?

Don't go there.

To do that properly would need a minimum of 5 years experience working as an electrician full time. Preferably more.
It's an area where getting some piece of paper from a course means almost nothing. Most of testing and inspection is the inspection part, and you can't learn that in a classroom.