Frank Erskine wrote:

One thing I would like to find is heat-resistant blue and brown
conductors to replace burned-out/charred wires in loads of
chandelier-type theatre-foyer installations, without bits of
silicon-rubber sleeving.


How high do you want to go with the temp resistance? RS (rswww.com) have
several high-end single-core wires you might be interested in. There's a
glass-fibre-covered silicone wire, temp-rated to 150 C continuous, in a
6A and a 15A rating. Catalogue nums 381-731 and 381-747 respectively
(though they've just changed suppliers and those particular partnums
have been replaced by others, which come without a datasheet). If that's
still too wimpy, move up to furnace-friendly
PTFE-in-glassmica-in-glassbraid, partnum 359-560 - a snip at 40 notes
each 10m reel (or a bargain 150 notes if you buy 50m) - this is the
smallest guage in that range, a 1mmsq rated to a paltry 25A ;-)

Rather less exotically - and in the blue and brown you ask for, instead
of all one 'natural' colour - is PTFE-insulated wire in various guages,
such as 365-795, 6A rated, 27notes for the 100m reel, alleging temp
rating up to 200C.

The exotics mentioned first are under Cable&Connectors - Cables -
Specialised Industrial Wires and Cables; the more useful ones (and
there's quite a range) are at Cable&Connectors - Cables - Equipment
Wire, in several subsections, most of which mentions "high temperature"
or similar.

HTH - and keeps your theatres safe ;-)