I wish to add a comment to what I said above about Travelex. Their airport kiosks usually have the worst deals around. I have this habit of taking photo of the boards with the rates to compare various places in the country.
However I recently discover that their online deals appear pretty good. You essentially book everything online at a guaranteed rate. The website shows an excellent exchange rate (better than BoC when I looked) and no fee. You essentially get an option as you can cancel. You do the actual exchange at the airport or some locations in cities. Have not tried yet but looks good: https://buy.travelex.com.cn/encn/Pur...Result=1219301