User Activity

I have just been charged import charges for an item from the US. I was of the belief no import charges are applicable for items less than $100.
I just purchased articles in Canada and when I paid via PayPal I was charged GST and I see I have just been charged by Ebay additional GST (Australia) - why?
I constantly reset my EBay page to my postcode and the way I prefer the page displayed, however, it keeps reverting to a Qld post code and displaying only 50 items in Besat Match. Not what I prefer. How can I prevent this from happening?