Hey JANorton - nice work on the new civ.
I want to say that it looks way overpowered imo, even without any UU as you say. Bear in mind that most civ's UU/traits are only useful for small portions of the game. Dont forget that all UU's either obsolete quickly, or are unavailable for a long time.
I have a couple of simple suggestions, which I have tried to keep in line with the flavor of an Aussie civ:
Circus - The way I play civ, this is an essential building in every city that can hold one, the happiness bonus is too good to miss, happiness being a much more sought after commodity in Civ V. This Showground design is way better, you can build it more often, and it bestows a production bonus (production is also more highly valued in Civ V), its just going to be awesome. Period. Does that not break the balance though? What I would suggest, is if this showgrounds represents a farmers market type structure, that it benefit commerce in addition to happiness, not food or production. Suggestion: make the bonus of the SHOWGROUNDS +3 happiness, +2 gold for all sheep/horse/cow resources within city boundary.
Worker - Essential unit for the entire game. Every civ has these, they are never obsolete, they are available from the dawn of man! The +50% rate of the convict worker is a breaker for me, makes them far too powerful. Plus, it devalues any wonders/policies which would add to worker work rate. The fact that they are cheaper (50 base rather than 70) is a bonus enough. Did convict workers actually build things 50% faster?! Makes more flavour sense in my opinion, for them just to be easier to mass produce quickly and cheaply. Suggestion: make the base cost of the CONVICT WORKER 40 rather than 70, effectively costing almost half of the normal price, remove the +50% work rate.
Hope you take the feedback in the spirit they are intended, I like the ideas, the graphics, the flavour so far, just think the bonuses are overpowered, possibly to the point of breaking multiplayer/or even single player where you do not get to play as Australia!
cheers