Well don't know what programme culturemuncher was watching but it was made up old tosh...
Lots of modern varieties have come out of New Zealand not Australia
Root stocks don't influence flavour they influence the tree's ability to crop and how vigorously they grow (one that controls growth for good soil, something that allows more growth for poorer soil, entirely natural, these were developed in Kent at East Malling Research and every fruit tree in a commercial orchard worldwide grows on them)
Whilst lots of modern varieties do have relatives like Goldens, most are related to gala or Braeburn (Rubens, Kanzi, jazz etc) only light coloured ones are likely to be closely related to Goldens, something like Opal or Amelia
There are 1000's of varieties available, most aren't grown commercially because they taste foul, grow 3 apples once every 9 years, don't store or look awful
Sainsburys is probably your best bet for a range of varieties (52 different apple varieties sold in the last 12 months) they always have russet in season, they also usually have the first discovery in August
Can you tell what I do for a living 
Personally I think that discovery are about as foul as Goldens and Granny Smiths, sorry Elfycat and the other fans, they taste like soap unless you get them straight form the tree (their big win for me is that you can tell when they are ready to eat as the orchard smells gorgeous)
Spartan, Zari and Rubens are my favourites beautiful to look at, taste fantastic and you can cook/juice them
British are best, always, just think how far the others have travelled...