C-Wire for a Vulcan Gas Central Heater for Nest Thermostat-E

I'm hoping the friendly people here could help me. I'm looking to purchase a Nest Thermostat-E but my current thermostat (Vulcan/Bonaire Summer Breeze) only has 2 black wires connected.

I've searched around and asked for advice and I've heard some people say it will work with just 2, and some say I need a C-Wire.

Given the opportunity, I think it best to run a C-wire if possible, I have uploaded images of the Heater unit and it seems as though the 2 wires from the thermostat connect to the (green) 2 x "Heat" terminals and I assume the 2 x "Cool" terminals are for Air con if I had it.

Now my question is, is the single 24v terminal used for the C wire? And if so, what would the 2x black wires be named when connecting to the Nest Thermostat?

It also looks like there is a piece of wire connecting the 24v connector to the 2nd heat port, what is this for and do I need to keep it there?

If this is not possible, can I/ do I need to connect directly to the board?

The heat I have is a Vulcan Tubular Central Heater – V3 20i Internal NG : Part #5310052

If it makes a difference, this is in Australia.

Thank you all!

More Images are here: https://imgur.com/a/WveSexP

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