There's both bad news and good news and here it is:BC639/640 from NXP/Phillips are a good bet if you can get them anymore.
N comes before the P means you select the lower numbers before the higher numbers................If BC550C is the NPN part then that's what it should be. I mix them up all the time! Must fix that...
So if I understand correctly 240VAC->340VDC. 30mA*220R=6.6V. So I have 13.4V to work with.
Merlin, what do you think about this? The 220R/220u RC is from your supply. It took some determination to make it safe from overvoltage and inrush current, but I like how it turned out.
Don't put more than 330uF between the Kmultiplier and the HV2. Capacitance after the HV2 is okay because it will be limited to 30mA inrush.
I just realised it might be far easier and more effective to replace the string of diodes with a 12V zener, so this would drop about 12.7V ? So 21V in and 8.3V out. This would be fine for my application. Would the higher voltage drop cause any issues, except of course the need for a heatsink on Q2 ?