So this project works fine BUT all but two of the driver IC's I have turned out to be fakes.

I've done a bit of research and it looks like I can achieve pretty much the same thing with a microcontroller.

I've ordered a few PIC16F18446-I/P and wil redesign the board for these. I'll use 8 inputs and 9 outputs. pins.

7 of the outputs will drive segments and the 8th and 9th outputs will select which of the two digits will be lit. 

The GPIO outputs can handle plenty of current but I'll be limiting that with a resistor anyway. I can connect the digit select output pin to the common cathode of one digits so when the digit select pin is low then it will be enabled and the digit lit. 

The data sheet is massive and I've never used a microcontroller so there is an excellant chance that I've misunderstood this device. 

Datasheet page 629 has the electrical specs https://ww1.microchip.com/downloads/en/DeviceDoc/40001985B.pdf 

If this approach works then it's actually a singe chip solution I think unlike the current design.

The other advantage is that the PIC16F18446 device is really cheap and available. I ordered direct from the manufacturer but there a deilivery cost so I ordered 5 or 6 of them; enough for 12 digits.