[Arran]

 Two .01 uf 630 vdc caps is .005 uf 1260 vdc in series, I take it this one is a tone compensation cap across the output transformer primary? The electrolytic is probably a bypass connected in parallel with the bias resistor on the audio output tube, if so then 22 uf at 20 vdc is fine, in fact you could use pretty much anything there if it's at least 20 vdc, 20 volts is sort of an odd voltage rating for a small electrolytic anyhow, sort of like finding a 1/3 watt resistor.
Regards
Arran