[michaelt]

Don't most UK houses also have earth bonded to all the water and gas pipes in the house?

There may be no earth spike, but if earth connects to a copper pipe going into the ground, you'd expect them to be at the same potential.

[jon_adler]

I believe metal pipe bonding is a building control requirement however many new builds use predominantly plastic pipe work. The requirement is to protect the occupant against touching live metal pipe work, not to earth the house.

[yrro]

Gas pipes can't be plastic!