TheOldFellow wrote:

See http://www.langside.f2s.com/web-oso.jpg
[...]
The Oftec fitter wired in the thermostat using heat resistant flex and a
white plastic "strain relief" or maybe it's a "gland". Where can I get one
like it? Nothing on TLC looks the same.

That looks like a Heyco strain relief bush. Heyco are now part of
Anixter Components, so try
http://www.anixtercomponents.com/all...l &language=2
(look at the "straight-thru" bushes).

Heyco bushes can be quite a fiddle to fit if you haven't got the magic
tool, so a conventional stuffing gland - like wot Owain suggested -
might be a better bet in any case.

--
Andy