I think there may be a little confusion here. As you've been told, in the context we are talking about, impedance and resistance are, as near as makes no difference, identical - so the resistance measurements you have undertaken are perfectly OK in terms of confirming satisfactory connection of the CPCs etc. within your house..
What you do not have the equipment to do is to test the impedance of the entire 'fault loop', which includes the impedance of the earth (external to your house).
In fact impedance (which is what 'impeded' the flow of AC current) is a combination of two elements - resistance (exactly the same resistance that would be relevant if the current were DC (i.e. as you have measured) and reactance. The latter will be nearly zero for cables/conductors in a domestic 50Hz AC installation - so, as has been said, impedance would (numerically) be essentially identical to the resistance (such as one would measure using DC).