Thank you very much for the list, makes buying the remaining few items I need a lot easier too!
Not entirely sure that the cast aluminium plate specified in the voron build is any better than yours, the manufacturing specification there calls for .015" for 'flatness'. This translates to 0.381 mm. This aluminium plate is actually a part of the build that bothers me. Aluminium cannot easily be ground flat like steel on a surface grinder (the aluminium melts itself into the grinding wheel) which means a fly cutter is used, afaik, to machine it flat. For this type of machining 0.2mm deviation would probably be acceptable, especially on the sides/corners of the plate where there would be an interrupted cut.
It may make sense to buy a larger plate, have it machined, then cut it down to size to circumvent this. This would probably be the case in the mic-6 type tooling plate specified for the voron build, that is, unless you end up with a piece from the side or corner of the larger plate it was cut from.
Quality float glass is a lot 'flatter' than that. Float glass obviously does not have the thermal coefficient of aluminium and would take more time to heat up AND requires a decent heat spreader attached to it to ensure even heating. It also presents more of a challenge in mounting but the voron setup, being a fixed print bed solution, lends itself to many more mounting options. Usually a thinner sheet of aluminium is used for the heat spreader under glass print beds, but given its thickness, it's likely that the aluminium would warp, creating cold/hot spots on the glass print bed it is attached to.
So, at least in my amateur opinion, if the heat spreader problem can be solved (graphite?) glass would make for a much more readily available solution. Note that I am being speculative here, mostly because the courier shipping cost of mic-6 aluminium plate is easily double that of the plate itself, pushing the total cost for this part alone over R1500.