very well put. but, to take it a little bit further, if , say, fitting an extra socket or whatever, and issuing a MWC, you could , on that MWC, state clearly " the installation should now have a full inspection report. " by doing so, though, you are implying that the installation may be unsafe, scaring the customer, and worst of all, shooting yourself in the foot in the customer's eyes as you are the expert and should ensure that the installation is safe.Absolutley, of course I would bring it to the attention of the householder. But my point is that you cannot be held legally responsible for failing to report the danger. It is very possible you would not be aware of this danger - or anything else that may be an immediate cause of danger. The Danger Notice is one way of bringing to the attention of the client anything you may notice, but it won't protect your bum because your bum does not need protecting.
The moral issues are, of course, a different kettle of fish, but you can't placate them by merely issuing a piece of paper. The Minor Works Certificate for the dimmer switch describes exactly what was done and may even recommend that the installation should be inspected.
By all means issue a Danger Notice to the client for the exposed cooker outlet, after all, he didn't realise it was dangerous. But what actually killed him was was the portable fan heater falling into his bath whilst plugged into the socket by the soap dish. He thought is must be OK because his electrician didn't give him one of those danger notice papers for it.
"but, your honour, I didn't see the socket....."
"I put it to you that you failed in your obligations because were more focussed on scaring your client into buying a new cooker when you should have recommended a full inspection report"
i may not have worded this in the best way, but what i'm trying to say is " how far do you go, when all mr. jones wants is an extra socket for his sky box.