OSG is a bit short on the wording...
BS6891 2005 section 8.16.2 "Separation of installation pipework from
"Where installation pipes are not separated by electrical insulating
material, they shall be spaced as follows: a) at least 150 mm away
from electricity meters and associated excess current controls,
electrical switches or sockets, distribution boards or consumer units;
b) at least 25mm away from electricity supply and distribution
Conduit or PVC L-angle (B&Q) is adequate to provide separation.