Fair enough concern. If you want to stick with plastic you need to stay with AWI, as little is available other than metal for F&IW. Uniforms were VERY different even though the conflicts were just over 10 years apart.
I still recommend first buying the 2nd generation rules, cards, and supplement covering the F&IW and the AWI. Then pick forces based on battle size you want and unit values.
Both the Perry's and Warlord have AWI plastic. From those two companies you can make units of Militia (warlord), British regulars, British light and grenadiers (Warlord), Hessian grenadier, fusilier, regular (warlord), native Americans, and Continentals.
You can also get artillery, but guns are not recommended for skirmish. I do use 3 pounders on occasion, but not often.
There is no plastic cavalry, but early Peninsular British Light Dragoons from Perry may be convertible. Never tried it though.
I live in Eastern US, and my county saw constant skirmishing as armies looked for forage. Fights involved militia and regular infantry per above and should provide enough for an endless set of games.
In Australia I would hope Warlord and Perry have suppliers even if on the other side of the world.