Using a silicon diode rectifier instead of an AZ31 valve

[Alan Douglas]

So, the consensus of opinion is that voltage equalising resistors should be fitted if two 1N4007s are used in series.

No censensus; they're not required, nor are "balancing" resistors for two series electrolytics. They are inherently self-balancing.

Regarding series electrolytics, I ran an experiment four years ago and posted the results in the Antique Radio Forum:
http://antiqueradios.com/forums/viewtopic.php?f=19&t=153805&p=1264569#p1264569
I just repeated it a few minutes ago (same capacitors, but at 550V) to get a new photo since the old one was lost.