BS8436 is available from Discount Electrical in cut lengths I believe.
It is about the same price as 3c SWA.

You must use a Type-B circuit breaker.
You can not use a rewireable fuse, BS1362 fuse or Type C or Type D
circuit breaker.

You must use overcurrent protection matched to cable size.
You can only use 20A with 2.5mm radial and 32A with 2.5mm ring.

What this means is you can not wire a big 20A draw HVAC lump in BS8436
2.5mm and then use a Type-D 32A to get around the problem of nuisance
tripping on compressor startup current draw. Most domestic HVAC are
relatively small or in duplicate (redundancy) or in series (air-to-
water heatpumps re getting outlet temperature high if not underfloor).

In 2011 or 2012 BS8436 from Prysmian will have 4mm added (32A radial)
and will all be 600/1000V in place of 300/500V currently. XLPE is also
set to take over from PVC (aimed at places stuffed with insulation re
grouping, temperature & insulation derating calculations).

Where would you use BS8436?
In a thin stud partition where you can not get 50mm from either side
and want to maximise floor space. I replaced a short run of SWA in
such a situation recently because it will get boxed in both sides and
the glands would not be accessible anymore for inspection & testing.