As yet, parts on order include:

Timing references, I can build this but better to buy a module.

Aixiz modules, I have the casings but not the "business end" holding the diode.

Instrumentation amplifers, I have 2 here but better to get a few spares as its quite a fragile part so will likely need to be socketed.

I may need to order some visible optimized lenses as the ones here aren't really ideal due to being set up for laser diodes not light input from quite a wide angle.

Parts I have:

HV supplies (3 known good, 1 a bit damaged but runs)

7* SBM-21 tubes

3* SBM-20 tubes

3* avalanche photo diodes (AD500)

Pi Zero W 

Assorted scintillators

Light tight casing for the diode assembly, ideally painted white so it keeps fairly cool.

LNB interfaces though can use an FM radio IC due to low bandwidth usage

2* red PT-54's complete with lenses and other ancillary parts

2* miniature Peltier modules