I've just been in a Boots chemist shop in Hua Hin where the cashier presented a small slip showing a HKD offered rate. I have a HK$1.23/mile offer for overseas currency spending (not to mention the rate offered was 1.7% over Visa rate after fees). A non-DCC slip was duly presented and happily signed for.

I have to settle the Sheraton bill when I get back to hotel but I expect the DCC override is a similarly easy walkover. I do not expect to have to stand over the cashier for 30 minutes like its Shenzhen cousin (though the reason I do this is night is to make sure I can do just that).