It sounds like it could be one of the things you describe. I can't say that the existing Earth is ok - just that there were no previous problems. I can say that the new earth IS earth, and that I haven't wired into an earth cable being used as live or neutral, as I am able to follow the circuit...
Wouldn't have a clue. I've never had to check voltage, so I don't have the means to do so.
Should I get it proffessionally checked, or get a voltage tester and pursue the problem myself?
I've just installed a set of LV kitchen downlighters as a spur from the lighting circuit. This was all very easy, nothing too challenging for an advanced DIY'er.
The problem arose when I wired up to provide their own switch to an existing wall box. The exisiting switch was earthed ok, so I...