On Fri, 24 Jul 2009 14:18:34 -0700 (PDT), Philip Oldrosedene
had this to say:

I wish to bring a remote CH motorized valve (Honeywell make) into
use. It wasn't connected when the CH was installed as the valve was
a last minute thought and no suitable cable was to hand. Up to now (8
years!) it has been left in the ON position.

Depending on route chosen, it will require 5 to 8m of cable to connect
to the main CH controller. The cable into the valve is 5 way x 0.8mm
sq (ie 1.0mm dia) - 4 control lines plus earth. The valve operates at
240V, so the cable needs to be rated for mains.

For preference I should like to use standard elec backing boxes to
house the connections at each end, and bury the cable run under the
wall plaster.

Please can anyone suggest a suitable cable & source?

If you can't get hold of 5 core cable you could use 2 runs of
'smaller' stuff, provided that you clearly sleeve the conductors with
divers colours to avoid confusion, and preferably document your choice
of colours for future reference.
(remembering of course to never use the ECC of a T+E for anything but
a true earth, since it has no insulation - merely a sheath!).

--
Frank Erskine