This was new to me - a requirement for a "trace wire" from water main
all the way into the house stopcock.

Trace Wire is attached to the mains water service pipe by means of
cable ties at intervals of not less than 1 metre. The purpose of Trace
Wire is to enable the location of the service pipe in the future. The
wire must be 1.5mm single strand BLUE plastic coated to 6491 standard
and installed on ALL installations.

Simon.