I purchased a box of 6 Acelux HF 700W Mercury Vapor Lamps and have 2 new 700w MV ballasts on order

aparently Voltage is the USA is 120V whereas Australia it is 240V

i was doing some reading and it appears that the Ballast doesent send 240v to the lamps anyway so would i have any issues using these lamps in australia?

Since your voltage is 240, your merc lamps need a choke up until 400w, then you need an autotransformer. In the us all merc ballasts are autotransformers. I think it would work, now you need to find a 700w ballast for 240 volt and a neutral. If you can't find a 240v ballast you could use a 120 one with a step down transformer.

Its a choke up to 1000W. Dont know about 2000W

For the 230V world I haven't seen anything else than a series choke and/or electronic. The only exception are ballasts for the US CWA rated lamps, where those are imported (heard only about Israel, likely due it's specific history).
Even the 3.5kW (the highest wattage for general lighting I've seen) are series choke, but designed to operate at 400V (connected between phases).
In most of the "230V" world the electricity is distributed as the complete three phase system with 230V between each phase and Neutral, then the 400V is available across the two phases.

Connecting complete power factor compensated fixtures on the 230V is highly not recommended, as with open Neutral fault the power factor correcting capacitors form nasty series resonators with the ballasts - yielding blown bulbs and ballasts (or at least fuses).
Therefore for higher power installations the compensation is usually removed from the individual fixtures and then connected just on the phase wires (the Neutral current is usually very small)

Higher wattage loads than 1kW usually means high power installation and that needs to be distributed symmetrically among the phases.
And with that becomes more practical to have the individual fixtures supplied from the 400V. It has two fold benefit: You won't need the Neutral conductor anymore (so it can not break), plus you have more voltage room to use higher arc voltage (lower arc current, so less lamp electrode losses for the same power).

Is that the overseas version of the U.S. 277-0-277=480 system? I've also heard of a 240-0-240 that yields 480.

The "240-0-240" with 480V is a 2 Phase X-0-X system at 180 deg Phase from each other, basically 2 in-phase 240V sources connected in series

The 277 with 480V is not an X-0-X system. There are 3 Phases with 277V, at 120 deg Phase from each other. The resulting sum voltage between 2 Phases is sqrt(3) times the voltage of Phase-Neutral, instead of double it, so 277 * sqrt(3) = 480

Here it is indeed a 3 Phase system as well, with the voltages :
220V L-N / 380V L-L
230V L-N / 400V L-L
240V L-L / 415V L-L

An apartment or a small house will normall only get one Phase and Neutral. so just 230V. A bigger house will get all 3 Phases, and an apartment complex will get all 3 Phasees with the apartments equally split between them

I didn't know that lighting could be connected phase to phase here in UK most industrial buildings have 250/433 volt supply's usually written as 440 volt I guess there must be tapped chokes to cope with this. I must ask a local electrician if it is allowed in the uk to connect t lights like this

The "240-0-240" with 480V is a 2 Phase X-0-X system at 180 deg Phase from each other, basically 2 in-phase 240V sources connected in series

This (and the 120-0-120/240) is not called "two phase", but "center tapped single phase".
Multilple phase (so two and more) naming is used only, when the phases are able to form rotational field, so the phase shift must be other than 180dceg.
There are two phase systems in use (as far as I know, only in the North America; as an industrial system), most of them mare based on a delta output of a 3-phase transformer, where one of the wires is grounded. So the result becomes one Neutral and two phase wires, with 60deg phase shift (if I calculate well). It still has a rotational field (for a 3-phase load connected to these wires), yet there are only two phases.

In the history was tried a 90deg phase shift system, in fact the first Tesla's concept (it is the most obvious way to mathematically describe rotating vectors: Just use two coordinates, "X" and "Y" and let each the phase voltage represent each of them).

It was only later changed to the more economical (but not that mathematically obvious) three phase system (same three wires, but with equal load sharing and lower voltage towards ground, so way cheaper or lower losses for the same construction and power level).

I've commonly sen wye and delta setups hree in the U.S.  most houses will get 120-0-120. 120 for regular devices and 240 for furnaces, stoves, ovens, etc. I have seen larger houses that pull in 208 or 277 for HVAC or illegal things.

As far as I understood, other than the 120-0-120/240 is used mainly for industrial purposes.
I would say rather a mess there: 4 or 5 incompatible systems with very similar voltage levels (so addressing the same power needs)...