It has been happening to Australians buying from the UK too.....the first time it happened to me was about October 2014 when I was buying diaries for Xmas.  It happened again in 2015 so obviously nothing has been done.

And to make matters worse the Shopping Cart only works intermittently....it cost me an extra $10 shipping because I could not combine two higher value items from Bing Lee when using the discount voucher last week.