I don't think that there's a nozzle offset issue, since I've verified Z=0.8 is indeed 0.8mm via gauges.
I've also set the z=0 print gap with a 0.04mm and 0.05mm feeler gauges, which had no effect.
Also, still not having any issues when using an E3DV6 loaded with a 0.4mm nozzle and 0.2/0.3/0.35 layer heights.
I did however try 0.5mm layer heights again, which actually needed the flowrate dialed down to 60% in order to print the first layer correctly.
Printer is in use at the moment and the trash was thrown out - once it's done I'll have to make a bad layer 1 to take pictures of.