[morzh]

Arran

Yep, the 8-pin keyed socket. All the pinouts are eaisly seen in Radiomuseum's pages.
I won't be able to test them but will presume tthey are working tubes as Peter has the video of the set working. One tube was out of socket when it arrived but I hope it did not bounce much as it was immediately glued to the speaker's magnet (Stahl !!! High iron content.)

The doubler takes two diodes and so creating a tube one is out of the question.
I have already written about trying to use bridge rectifier, as, again, I do not have space for an extra capacitor either (it takes two caps and two diodes to double in Greinacher circuit). The bridge will effectively double the DC level (2/3 peak vs 1/3 peak) vs half-wave and the RMS is 40% higher also.

And the caps is probably not a bad idea either, as even in the original circuit with 220VAC there will be at least 7W dissipation to ballast the 220V to the needed 150V (they have 700 ohm resistor at 100mA).

I will use that Simran of mine together with the Variac to achieve 220V (I have 240V out). Though I see additional, not accounted in the sch, 70 Ohm resistor. The big green one, it is on the photos. I wonder if it was put there for that very reason: the voltage in Europe is also a bit higher than 220V.