Fredxxx wrote

This is 24V and need to cable up between closer and switched supply.

I have checked the supply does go off with a fire alarm!

What cable should I use?

Whatever will handle the current without dropping too much voltage.

I'd normally use what we call Figure 8, because it is
readily available and has plenty of copper so that
it wont drop too much voltage at any current that
is likely in that situation and quite cheap because
its sold in very high volume.

http://static.rapidonline.com/catalo...17214P01WL.jpg

I'd rather use something other than mains cable
to differentiate between mains and ELV.

Makes more sense to use a different color.