First thing I did was to check the bonding which was as it should be. Next thing was to check that the pme earth was as it should be. Ze was good so I was pretty sure that the raised potential was on the gas pipe. To be doubly sure I connected my wander lead to the pme terminal and then took a voltage reading on two different pieces of metalwork on the street (it was raining) - pme terminal to railing 1V, disconnected gas pipe to railing 6V so I was happy the raised potential was on the gas incomer. The electric supply was underground and shared, the neighbours being looped off so there should have been a rod either out the front or back but I couldn't see one. Reported the issue to WPD and had another very quick response but the neighbours were not in so they couldn't gain access. However, they scheduled a job to do an underground joint and supply both properties with concentric to enable both to have pme, one of the working theories being that next door's earth may well be through the gas pipe.
Meter fitter regained some colour and advised he was going to tell his colleagues the importance of the big lead with the two croc clips on it