Unfortunately sound travels through structure as well as air. In fact sometimes better through structure depending on the frequency. We have used a product called Regupol which is a recycled rubber mat product that has great sound deadening qualities. However in your situation the existing floor boards would need to be removed, a thin sheet of ply laid down and then the Regupol placed on the ply before relaying your existing floor boards. this would give separation from the floor joists and your floor boards. Filling the cavity with an insulation type product or egg creates will not give you the desired affect. Have a look here http://www.regupol.com.au/au/

im also in adelaide and trying to work out what exactl defines ”semi-detached”. is the roof shared between two dwellings or do they look like two separate houses with just a shared wall? also, does the shared wall go all the way along rhe entire length of the house or do they just share the wall between garages?

As the house is in a rural setting, a colour which blends in with the bushy environment would look best. A greenish-grey would look good, such as Linseed or Oyster Linen or even Bears Foot, as suggested above. I'm sure there are many more suitable colours to choose from and it would be a good idea to buy a few sample pots to test first.

I will be the loan naysayer and go: Vinyl Plank timber pattern tiles. I did these in my kitchen and they helped make the room. Used Karndean, but any European brand should be fine (avoid American and assume they are using American or worse if they don't say the country of origin). http://www.karndean.com/en-au/floors/landing-pages/new-looselay-longboard?gclid=CjwKCAjwspHaBRBFEiwA0eM3kQ7eEFPH5FlK2IwV3o7ZsbbmJ19srG0OM_tWK5dhPMNyDdwxGPUr4BoCoYcQAvD_BwE Caveats: Ground must be FLAT. 100% flat, ruler FLAT. If not you will have to level. If flat, you can lay them yourself. Our floor had to be levelled and it was tough. still got a few high patches and gaps because of that. However I have done it on a concrete surface myself since and it's beautiful. Benefits: Nice and soft on the foot. (less ankle pain) single tile replacement. Looks fantastic. No PVC glue fume issues and fairly resilient. Do be wary though of metal chair legs scraping the floor. Waterproof! when installed right with no gaps! (why I would choose them in a kitchen over timber or Eeek carpet!.... Yes previous owner installed shagpile carpet in the kitchen).