Hey man, Im also an American in London but i'll share with you what works for me...
What I like to use is a little butt bump. You see a girl you are interested in you dance around them and bump your butt into their butt. Just don't do it too hard! But it should def get her attention. Now you can do 1 of 2 things:
1. Bend a bit at the knees while leaning a bit back. Extend both your hands towards her, palms facing up with a sly grin cheeky smile. They will usually grab hold, but if she doesn't then try it on someone else.
2. With you main hand gesture for a high five. When they high five you back (they almost certainly will, unless shes a huge bitch-->who wants her anyways then??), you grab hold of her hand and spin her. That automatically gets you dancing with her and you can do whatever from there like say "show me your moves

"
Hope this helps, but it should def get you started. Good luck in Australia, the girls are quite hot there i hear!