Leave the PEB connections as they are. Switch off all power, disconnect the main earthing conductor at the CU: check no voltage is present first!
Then connect your flying leads to the earth and live/ neutral at the main switch.
This should give you a Ze.
Will switching off at the main breaker on the CU suffice? Switching off anywhere else will be a bit of a challenge.
I will give this a go when I go back.
Couple of other things came to mind.
Could be anywhere between 10 and 20 metres of what looks like 16mm2 T&E between the meter and CU. If memory serves, the cpc is 4mm2 on these; it would provide an earth, but not exactly heavy duty, to say the least.
Can I run a separate 16mm2 from the CU back to the MET downstairs, and leave the existing T&E as it is?
How bad/legal/illegal is it to feed a CU with a long 16mm2 T&E.
The downstairs neighbour asked me to have a quick look at her installation to see what I thought.
Meggar out, plug-lead in socket, Zs.............. 18
Started doubting myself and tester.
PFC test: ............13A
Repeated test in kitchen: same result.
Didn't think I was overdoing it by telling her she should consider having some work done in near future.
If this was gas, it would be a RIDDOR case.