Matt wrote in message m...

I'm about to install a ceiling fan that needs earthing.
Unfortunately my existing ceiling rose is not supplied with an
earth. I assume this means I need to find a separate earth to
attach - is it best if I find a cold-water pipe and bond to that?

Dear me, no. The first point is that if your wiring is of such an age that
the lighting circuits have no earth, then you ought to be thinking in terms
of a complete re-wire before too long.

A temporary solution is to run a separate earth (properly called a 'circuit
protective conductor' or CPC) from your fan back to the main earth terminal
in your consumer unit or fuse-box (near the meter). A water pipe should not
be used as a CPC because (a) you can't rely on its continuity after plumbing
alterations (plastic pipes, Speedfit fittings, etc), and (b) in old wiring
there's probably no main bonding to the incoming water service in any case.

And what kind of cable / markings should I use for the earth
connection - just single strand green / yellow?

For a separate earth like this you will need 4mm^2 green & yellow
single-core earth wire. The cable type is called 6491X, but just ask for "4
mil earth". You'll find that it has seven strands, not one, BTW.

Strictly speaking, to comply with wiring regs your earth should follow the
same path back to the consumer unit as the other wires in the lighting
circuit. However that probably won't be a practical thing to do and
ignoring it is a much more minor transgression that not having an earth at
all.

HTH
--
Andy