Ben Blaukopf wrote:

You need to bond the cold supply pipe with a 10mm wire (assuming a
standard electrical supply) back to the main earth block at the meter.
This is main bonding. By cold supply pipe, I mean the rising main, i.e.
the cold water pipe, within 600mm (I think, or something like that) of
where it enters the house (and it sounds like this is under the stairs).

You do not need to main bond anything else. If you do, then at best,
you'll just confuse the next person to look at the installation.

Gas pipe?