[Arran]

In Phico radios, pre 1939 ones at least, they used an early version of cloth push-back wire, there is no rubber under the cloth, other then what comes out of the transformers, and is attached to the filter caps. The original wire hook up wire was around 20 gauge, it's thicker then 22, but thinner then 18, I've used door bell or thermostat wire as a substitute, though I think you can buy a repro version of it, another option is Ceylonese covered wire like Brand Z used in their TV sets. For component leads you can go thinner, but I would not recommend it using thinner then 20 gauge for structural rigidity. When it comes to stranded wore I usually end up using 18 gauge for things like speaker cables, it's hard to get stranded wire where I am any thinner then that, the only local source is auto parts stores.
Regards
Arran