The voltage-operated elcb system is now obsolete, their use has been prohibited under IEE regs since the mid-1980s.
They were never that popular in this part of the UK, probably due to local soil conditions. I've seen very few of these devices in service, by far the most common method of earthing I find in older rural installations is PME (TNC-S) where the main earth is terminated in the supply company's neutral block.
A large proportion of older installations are only earthed via the water pipe, which can provide surprisingly good (low) earth loop impedance values, providing all the supply pipes are still metallic. This method of earthing is also now (since 1966) prohibited, although equpotential bonding of metallic service pipes is mandatory.
Where I find old installations without suitable TN-S or TNC-S earthing facilities, the local PoCo will provide an earth terminal, usually free of charge.
