It strikes me that a functioning VOELCB could be the answer, but only if:-

• All incoming services are plastic, or have plastic inserts.
• The VOELCB breaks all incoming wires, including the earth (so 3-pole or 5-pole).
• The VOELCB has a properly independent earth rod as its reference.

The moment that the incoming PEN drifts too far from real earth, the power would be completely shut off.

 Simon Barker you've made some great suggestions, and believe me, I've looked at this in great detail, but there are still some issues.

It's not just incoming services that would have to be plastic ... there are a number of structures with substantial amounts of steel, which are extraneous-conductive-parts too.

And this leads into the second issue of a VOELCB, which is where to put a suitably segregated earth electrode so it's looking at "true earth".

There actually are some modern VOELCBs that have a measurement earth electrode out there on the market, it's just looking at how we use them, which has been the difficulty with their use for many EV charging installations.

 Simon Barker you've made some great suggestions, and believe me, I've looked at this in great detail, but there are still some issues.

It's not just incoming services that would have to be plastic ... there are a number of structures with substantial amounts of steel, which are extraneous-conductive-parts too.

And this leads into the second issue of a VOELCB, which is where to put a suitably segregated earth electrode so it's looking at "true earth".

There actually are some modern VOELCBs that have a measurement earth electrode out there on the market, it's just looking at how we use them, which has been the difficulty with their use for many EV charging installations.