"froggers" wrote in message
...
What I'm after really is an idea of the size of wiring I need to use
to
extend the ring (I'm planning on just breaking into it at an
existing
socket, and then taking one wire to a new socket, and then joining
the
two
sockets together to rejoin the ring).


2.5mm


A spur for a double ganged socket outlet should be wired from a ring main
in 4 mm (or
bigger) cable
or, alternatively, continue the ring through the new socket, IMHO.

You could use 4mm but 2.5mm will do.
4mm would be needed for a radial circuit though.